NFC: TreeTransform.h: make the function TransformNestedNameSpecifierLoc more beautiful

Hi,
I am new to LLVM, and I really want to get involved in LLVM community.

I guess if the following switch case of function
TransformNestedNameSpecifierLoc could possibly made more beautiful with
'break' stmt moved inside of the right brace.

I think move of 'break' stmt will not change the invoking destructor of
IdInfo.

Thanks for your effort.

I have done make check-all on x86_64-linux
Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D102577