[Clang][CodeGen]Remove anonymous tag locations

Remove anonymous tag locations, powered by 'PrintingPolicy',
@aaron.ballman once suggested removing this extra information in
https://reviews.llvm.org/D122248
struct:

  struct S {
    int a;
    struct /* Anonymous*/ {
      int x;
    } b;
    int c;
  };

Before:

  struct S {
    int a = 0
      struct S::(unnamed at ./builtin_dump_struct.c:20:3) {
        int x = 0
      }
    int c = 0
  }

After:

struct S {
  int a = 0
    struct S::(unnamed) {
      int x = 0
    }
  int c = 0
}

Differntial Revision: https://reviews.llvm.org/D122670