rustdoc: remove unneeded CSS td, th { padding 0 }

This was added in 5101078, to fix
the display of the module items and search results tables (see the discussion
in #86725).

Those aren't tables any more. The only remaining table is in docblock, which
has its own padding declarations.

Author: notriddle

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

@@ -299,11 +299,6 @@ summary {
 
 /* Fix some style changes due to normalize.css 8 */
 
-td,
-th {
-	padding: 0;
-}
-
 table {
 	border-collapse: collapse;
 }