Remove stale sentence from attribute docs

rules/private/diff_test_private.bzl

@@ -136,9 +136,9 @@ def diff_test(name, file1, file2, **kwargs):
     """A test that compares the contents of two files.
 
     The rule compares the files at build time. If the files match, the rule
-    writes a dummy platform-specific script (.bat file on Windows, .sh on other
-    platforms) that just exits with 0, and which is the actual test script. If
-    the files do not match, the rule fails to build.
+    writes a dummy platform-specific script (`.bat` file on Windows, `.sh` on
+    other platforms) that just exits with 0, and which is the actual test
+    script. If the files do not match, the rule fails to build.
 
     (The comparison is done at build time, not test time, because it makes the
     rule easier to implement.)
@@ -147,8 +147,6 @@ def diff_test(name, file1, file2, **kwargs):
       name: The name of the test rule.
       file1: Label of the file to compare to <code>file2</code>.
       file2: Label of the file to compare to <code>file1</code>.
-        be the same or not. The test passes if this is True and the files are
-        the same, or if this is False and the files are not the same.
       **kwargs: The <a href="https://docs.bazel.build/versions/master/be/common-definitions.html#common-attributes-tests">common attributes for tests</a>.
     """
     _diff_test(