clang-format: [JS] Fix missing space after 'yield'.

Before:
  class X {
    delete(val) {
      return null;
    }
    * gen() {
      yield[1, 2];
    }
    * gen() {
      yield{a: 1};
    }
  };

After:
  class X {
    delete(val) {
      return null;
    }
    * gen() {
      yield [1, 2];
    }
    * gen() {
      yield {a: 1};
    }
  };

llvm-svn: 285569