[llvm-branch-commits] [NFC] [FlowSensitive] Fix missing namespace in MockHeaders (PR #170954)

[Florian Mayer via llvm-branch-commits]

https://github.com/fmayer created https://github.com/llvm/llvm-project/pull/170954

This happened to work because we were missing both a namespace close and
open and things happened to be included in the correct order.