Remove horizontal lines at top of page

They are not needed to separate the search bar and the title, which are
visually distinct on their own.

src/librustdoc/html/static/css/rustdoc.css

@@ -148,8 +148,6 @@ h1.fqn {
 }
 .main-heading {
 	display: flex;
-	border-bottom: 1px dashed #DDDDDD;
-	padding-bottom: 6px;
 	margin-bottom: 15px;
 
 	/* workaround to keep flex from breaking below 700 px width due to the float: right on the nav
@@ -785,7 +783,6 @@ nav.sub {
 
 nav.sub {
 	flex-grow: 1;
-	padding-bottom: 10px;
 	margin-bottom: 25px;
 }
 .source nav.sub {

src/librustdoc/html/static/css/themes/ayu.css

@@ -194,9 +194,6 @@ pre, .rustdoc.source .example-wrap {
 pre.rust .comment { color: #788797; }
 pre.rust .doccomment { color: #a1ac88; }
 
-nav:not(.sidebar) {
-	border-bottom-color: #424c57;
-}
 nav.main .current {
 	border-top-color: #5c6773;
 	border-bottom-color: #5c6773;

src/librustdoc/html/static/css/themes/dark.css

@@ -151,9 +151,6 @@ a.result-keyword:focus { background-color: #884719; }
 pre.rust .comment { color: #8d8d8b; }
 pre.rust .doccomment { color: #8ca375; }
 
-nav:not(.sidebar) {
-	border-bottom-color: #4e4e4e;
-}
 nav.main .current {
 	border-top-color: #eee;
 	border-bottom-color: #eee;

src/librustdoc/html/static/css/themes/light.css

@@ -148,9 +148,6 @@ a.result-keyword:focus { background-color: #afc6e4; }
 .content .fnname { color: #AD7C37; }
 .content span.keyword, .content a.keyword, .block a.current.keyword { color: #3873AD; }
 
-nav:not(.sidebar) {
-	border-bottom-color: #e0e0e0;
-}
 nav.main .current {
 	border-top-color: #000;
 	border-bottom-color: #000;

src/test/rustdoc-gui/headings.goml

@@ -15,7 +15,6 @@
 goto: file://|DOC_PATH|/test_docs/struct.HeavilyDocumentedStruct.html
 
 assert-css: ("h1.fqn", {"font-size": "24px"})
-assert-css: (".main-heading", {"border-bottom-width": "1px"})
 
 assert-css: ("h2#top-doc-prose-title", {"font-size": "20.8px"})
 assert-css: ("h2#top-doc-prose-title", {"border-bottom-width": "1px"})
@@ -55,7 +54,6 @@ assert-css: ("h6#sub-sub-heading-for-struct-impl-item-doc", {"font-size": "15.2p
 goto: file://|DOC_PATH|/test_docs/enum.HeavilyDocumentedEnum.html
 
 assert-css: ("h1.fqn", {"font-size": "24px"})
-assert-css: (".main-heading", {"border-bottom-width": "1px"})
 
 assert-css: ("h2#top-doc-prose-title", {"font-size": "20.8px"})
 assert-css: ("h2#top-doc-prose-title", {"border-bottom-width": "1px"})
@@ -115,7 +113,6 @@ assert-css: (".sidebar .others h3", {"border-bottom-width": "0px"}, ALL)
 goto: file://|DOC_PATH|/test_docs/union.HeavilyDocumentedUnion.html
 
 assert-css: ("h1.fqn", {"font-size": "24px"})
-assert-css: (".main-heading", {"border-bottom-width": "1px"})
 
 assert-css: ("h2#top-doc-prose-title", {"font-size": "20.8px"})
 assert-css: ("h2#top-doc-prose-title", {"border-bottom-width": "1px"})
@@ -148,7 +145,6 @@ assert-css: ("h6#sub-heading-for-union-impl-item-doc", {"border-bottom-width": "
 goto: file://|DOC_PATH|/test_docs/macro.heavily_documented_macro.html
 
 assert-css: ("h1.fqn", {"font-size": "24px"})
-assert-css: (".main-heading", {"border-bottom-width": "1px"})
 
 assert-css: ("h2#top-doc-prose-title", {"font-size": "20.8px"})
 assert-css: ("h2#top-doc-prose-title", {"border-bottom-width": "1px"})

src/test/rustdoc-gui/toggle-docs-mobile.goml

@@ -1,12 +1,12 @@
 goto: file://|DOC_PATH|/test_docs/struct.Foo.html
 size: (433, 600)
 assert-attribute: (".top-doc", {"open": ""})
-click: (4, 260) // This is the position of the top doc comment toggle
+click: (4, 250) // This is the position of the top doc comment toggle
 assert-attribute-false: (".top-doc", {"open": ""})
-click: (4, 260)
+click: (4, 250)
 assert-attribute: (".top-doc", {"open": ""})
 // To ensure that the toggle isn't over the text, we check that the toggle isn't clicked.
-click: (3, 260)
+click: (3, 250)
 assert-attribute: (".top-doc", {"open": ""})
 
 // Assert the position of the toggle on the top doc block.
@@ -22,10 +22,10 @@ assert-position: (
 // Now we do the same but with a little bigger width
 size: (600, 600)
 assert-attribute: (".top-doc", {"open": ""})
-click: (4, 260) // New Y position since all search elements are back on one line.
+click: (4, 250) // New Y position since all search elements are back on one line.
 assert-attribute-false: (".top-doc", {"open": ""})
-click: (4, 260)
+click: (4, 250)
 assert-attribute: (".top-doc", {"open": ""})
 // To ensure that the toggle isn't over the text, we check that the toggle isn't clicked.
-click: (3, 260)
+click: (3, 250)
 assert-attribute: (".top-doc", {"open": ""})