clang-format: Fix false positive in lambda detection.

Before:
  delete [] a -> b;

After:
  delete[] a->b;

This fixes part of llvm.org/PR21419.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221114 91177308-0d34-0410-b5e6-96231b3b80d8