clang-format: [JS] add space before operator 'in'.

Before:
  return ('aaa')in bbbb;

After:
  return ('aaa') in bbbb;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218119 91177308-0d34-0410-b5e6-96231b3b80d8