[Clang][Docs] use CommonOptionsParser::create instead of protected constructor...

[Clang][Docs] use CommonOptionsParser::create instead of protected constructor on libTooling tutorial (NFC) (#70427)

This patch fixes the code example on CommonOptionParser on
https://intel.github.io/llvm-docs/clang/LibTooling.html

CommonOptionParser's constructor is protected, and we can use
`CommonOptionParser::create` instead of that.
It seems like the LibASTMatcher tutorial already uses that.
https://clang.llvm.org/docs/LibASTMatchersTutorial.html



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Co-authored-by: Sirraide <aeternalmail@gmail.com>