rustdoc: remove no-op CSS `.search-results .result-name > span`

rustdoc: remove no-op CSS `.search-results .result-name > span`

The rule `display: inline-block` was added in
5afa52bc7dee683f25f437dddf338dbc6ad32eb8.
The `margin: 0` and `font-weight: normal` were added in
c01bd560e2f87a9a960ed071213edd70f73171a8.

Both seem to have been added to override class-based rules that were
targetted at method sections. See
<https://github.com/rust-lang/rust/blob/c01bd560e2f87a9a960ed071213edd70f73171a8/src/librustdoc/html/static/rustdoc.css#L140-L148>
for an example. The selectors that these were meant to override were changed
in a8318e420d19c364b1eec33956a86164941f6df4 and
76a3b609d0b93c5d8da5e4e3db37bd03e5cb1c30 to be more specific, so they no
longer need to be overridden.