build: fix clang-tidy plugin build failure

[scarf005]

Purpose of change (The Why)

/var/home/scarf/repo/cata/Cataclysm/tools/clang-tidy-plugin/TextStyleCheck.cpp:93:59: error: no member named 'equals' in 'llvm::StringRef'
   92 |         } else if( StringRef( SrcMgr.getPresumedLoc( SrcMgr.getSpellingLoc(
      |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   93 |                                   loc ) ).getFilename() ).equals( "<scratch space>" ) ) {
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~ ^
1 error generated.
ninja: build stopped: cannot make progress due to previous errors.

$ llvm-config --version
19.1.5

equals seems to be removed in recent LLVM (at least since 19) and thus it's not possible to build clang-tidy plugin.

Describe the solution (The How)

use equals_insensitive. see https://llvm.org/doxygen/classllvm_1_1StringRef.html#ae46058c90a3c703357331a6501b32f1c for details.

Testing

builds on local machine.

Additional context

for some reason LLVM doxygen isn't versioned so i can't find out which exact version removed equals.

Checklist

Mandatory

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax like closes #1234 in Summary of the PR so it can be closed automatically.
• I've committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.