clang-format: Allow braced initializers in template arguments of class

specializations.

Before:
  template <class T>
      struct S < std::is_arithmetic<T> {
  } > {};

After:
  template <class T> struct S<std::is_arithmetic<T>{}> {};

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237565 91177308-0d34-0410-b5e6-96231b3b80d8