[analyzer] Remove deprecated analyzer-config options

The `consider-single-element-arrays-as-flexible-array-members` analyzer
option was deprecated in clang-16, and now removed from clang-17 as
promised in
https://releases.llvm.org/16.0.0/tools/clang/docs/ReleaseNotes.html#static-analyzer

This shouldn't change observable behavior.

Differential Revision: https://reviews.llvm.org/D154481