test: Remove redundant comments from test files

Applies the same doc comment cleanup to test files:
- Removes test module headers (//! lines)
- Removes obvious test function comments
- Retains comments explaining non-obvious test scenarios

Test names should be descriptive enough to convey intent without
additional comments. Complex test setup or assertions that need
explanation retain their comments.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/mr_discussion_tests.rs

@@ -1,5 +1,3 @@
-//! Tests for MR discussion transformer.
-
 use lore::gitlab::transformers::discussion::transform_mr_discussion;
 use lore::gitlab::types::{GitLabAuthor, GitLabDiscussion, GitLabNote};
 
@@ -77,7 +75,7 @@ fn transform_mr_discussion_computes_resolvable_from_notes() {
     let result = transform_mr_discussion(&discussion, 100, 42);
 
     assert!(result.resolvable);
-    assert!(!result.resolved); // resolvable but not resolved
+    assert!(!result.resolved);
 }
 
 #[test]