clang-format: Fix incorrect lambda-detection.

Before:
  [ a, a ]() -> a<1>{};

After:
  [a, a]() -> a<1> {};

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@244890 91177308-0d34-0410-b5e6-96231b3b80d8