[llvm] [Utils] update_llc_test_checks.py: updated the regexp for ARM target (PR #148287)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

@Felle33 please can you investigate the CI failures:
```
2025-07-28T07:53:27.9753330Z Failed Tests (2):
2025-07-28T07:53:27.9753700Z   LLVM :: tools/UpdateTestChecks/update_llc_test_checks/aarch64-function-name.test
2025-07-28T07:53:27.9754265Z   LLVM :: tools/UpdateTestChecks/update_llc_test_checks/aarch64_generated_funcs.test
```

https://github.com/llvm/llvm-project/pull/148287