Make p tag "go with the flow". (#12998)

This commit sets the `p` tag to inherit whatever `font-size` and `line-height` are set on the `body` i.e., `.editor-styles-wrapper`. 
Currently the `p` tag here overrides a theme's most basic of font styles unless `font-size` and `line-height` are set on `p` in that theme.
And from what I've seen, being that specific on `p` is an uncommon pattern.

This also makes it easier and requires less specificity to style paragraphs on a per block basis by simply adding the font-size to the block container.

packages/editor/src/editor-styles.scss

@@ -6,8 +6,8 @@ body {
 }
 
 p {
-	font-size: $editor-font-size;
-	line-height: $editor-line-height;
+	font-size: inherit;
+	line-height: inherit;
 }
 
 ul,