[clang-tools-extra] [clang-tidy] Improve redundant-casting check for binary operation (PR #191386)

[Baranov Victor via cfe-commits]

vbvictor wrote:

The correct diagnostic would could be (I didn't check proper regex):

"warning: redundant explicit casting to the same type 'size_t' (aka '{{unsigned}}') as the sub-expression, remove this casting [readability-redundant-casting]"

Some other tests may need correction as well, I checked only one

https://github.com/llvm/llvm-project/pull/191386