Fix duplicate usage of a article.

This fixes a typo first appearing in rust-lang#94624
in which test-macro diagnostic uses "a" article twice.

Since I searched sources for " a a " sequences,
I also fixed the same issue in a few source files where I found it.

Signed-off-by: Petr Portnov <gh@progrm-jarvis.ru>

crates/ide-db/src/imports/merge_imports.rs

@@ -225,7 +225,7 @@ fn path_cmp_short(a: &ast::Path, b: &ast::Path) -> Ordering {
 }
 
 /// Compares two paths, if one ends earlier than the other the has_tl parameters decide which is
-/// greater as a a path that has a tree list should be greater, while one that just ends without
+/// greater as a path that has a tree list should be greater, while one that just ends without
 /// a tree list should be considered less.
 pub(super) fn use_tree_path_cmp(
     a: &ast::Path,

crates/rust-analyzer/src/bin/logger.rs

@@ -132,7 +132,7 @@ where
 
             let ext = span.extensions();
 
-            // `FormattedFields` is a a formatted representation of the span's
+            // `FormattedFields` is a formatted representation of the span's
             // fields, which is stored in its extensions by the `fmt` layer's
             // `new_span` method. The fields will have been formatted
             // by the same field formatter that's provided to the event