[clang] [AST] Bump Type::NumOfBuiltinTypeBits. NFCI. (PR #113559)

[Jay Foad via cfe-commits]

jayfoad wrote:

> The community doesn't add new builtin types particularly often, so having four leftover bits isn't actually that close to the limit for us.

I guess "close" is subjective.

> Is there a problem with keeping this change downstream until we get to the limit in community?

No, I was just trying to separate out some changes that seemed upstreamable.

https://github.com/llvm/llvm-project/pull/113559