servo: Merge #11329 - Report use statements that use {} with only one entry (from c-rhodes:11320); r=jdm

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [X ] `./mach build -d` does not report any errors
- [X ] `./mach test-tidy --faster` does not report any errors
- [X ] These changes fix #11320  (github issue number if applicable).

Either:
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process.

Source-Repo: https://github.com/servo/servo
Source-Revision: 2f9796fa696e9514280777398467696dd4f004b3

servo/python/tidy/servo_tidy/tidy.py

@@ -390,6 +390,8 @@ def check_rust(file_name, lines):
             # No benefit over using &str
             (r": &String", "use &str instead of &String", no_filter),
             (r"^&&", "operators should go at the end of the first line", no_filter),
+            (r"\{[A-Za-z0-9_]+\};", "use statement contains braces for single import",
+                lambda match, line: line.startswith('use ')),
         ]
 
         for pattern, message, filter_func in regex_rules: