0b1c8fd162
This is an oversight from https://github.com/llvm/llvm-project/pull/104817 where the intention was to hoist the ExternalASTSourceWrapper construction out of the conditional so it can be set on both the `SemaSourceWithPriorities` and be added as an external source to Sema. But the inner `ExternalASTSourceWrapper` allocation wasn't actually removed. This currently all works fine because all these AST sources are refcounted and point to the same underlying AST sources. But this patch cleans this up regardless.