internal: Fix rustdoc warnings

`cargo doc` generates a bunch of warnings on rust-analyzer. Fix all the
bare URL and empty code block warnings.

crates/test-utils/src/lib.rs

@@ -224,7 +224,7 @@ pub fn add_cursor(text: &str, offset: TextSize) -> String {
 /// Annotations point to the last line that actually was long enough for the
 /// range, not counting annotations themselves. So overlapping annotations are
 /// possible:
-/// ```no_run
+/// ```text
 /// // stuff        other stuff
 /// // ^^ 'st'
 /// // ^^^^^ 'stuff'