more clippy fixes:

clippy::search_is_some
clippy::redundant_static_lifetimes
clippy::match_single_binding
clippy::match_ref_pats
clippy::map_entry
clippy::manual_map
clippy::iter_overeager_cloned
clippy::into_iter_on_ref
clippy::extra_unused_lifetimes

crates/ide/src/syntax_highlighting/inject.rs

@@ -78,7 +78,7 @@ pub(super) fn ra_fixture(
     Some(())
 }
 
-const RUSTDOC_FENCE: &'static str = "```";
+const RUSTDOC_FENCE: &str = "```";
 
 /// Injection of syntax highlighting of doctests.
 pub(super) fn doc_comment(