[clang] [llvm] [analyzer][NFC] Remove "V2" from ArrayBoundCheckerV2.cpp (PR #126094)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

> Have you checked if anywhere in the docs or comments we still have "V2" somewhere?

I searched for `CheckerV2` and `BoundV2` and the only findings are:
- A annoying testcase called `test_demangle_pass` that contains references to many obsolete code fragments (in strings, as examples of mangled - demangled name pairs).
- The release notes and the checker documentation where I mention that `security.ArrayBound` was previousl y called `alpha.security.ArrayBoundV2`.

https://github.com/llvm/llvm-project/pull/126094