[clang-tools-extra] [clang-tools-extra] Remove 'REQUIRES: shell' from lit tests. (PR #156950)

[Baranov Victor via cfe-commits]

================
@@ -1,4 +1,4 @@
-// REQUIRES: shell
+// UNSUPPORTED: system-windows
----------------
vbvictor wrote:

Yeah, that's unfortunate.
I also found this in test results:
```
<testcase classname="Clang Tools.clang-tidy/infrastructure" name="clang-tidy-diff.cpp" time="0.00">
<skipped message="Missing required feature(s): shell"/>
</testcase>
```
>From [this](https://github.com/llvm/llvm-project/actions/runs/17517903882/job/49757841499?pr=157285) artifacts.

https://github.com/llvm/llvm-project/pull/156950