[clang-tools-extra] [clang-tidy] Add `readability-redundant-tag` check (PR #210007)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 3233 tests passed
* 34 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### Clang Tools
<details>
<summary>Clang Tools.clang-tidy/checkers/readability/redundant-tag.cpp</summary>

```
Test has no 'RUN:' line
```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/210007