[clang] Fix the double space and double attribute printing of the final keyword. (PR #88600)

[Vassil Vassilev via cfe-commits]

vgvassilev wrote:

IIUC, the PolishForDeclaration option is supposed to `When true, do certain refinement needed for producing proper declaration tag; such as, do not print attributes attached to the declaration. `. If the intent is to produce a forward declaration the `final` keyword cannot be attached to a forward declaration. So I am not sure what's the "right" fix here...

https://github.com/llvm/llvm-project/pull/88600