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

[Kim Gräsman via cfe-commits]

kimgr wrote:

> With .PolishForDeclaration=true, there are NO final specifiers (which is what we want to produce forward decls in IWYU)

This is actually a regression in this PR, and it breaks the clangd test added here: https://github.com/llvm/llvm-project/commit/9f57b65a272817752aa00e2fb94154e6eed1d0ec (the patch that originally led to double `final`s).


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