[clang] Fix printing of templated records. (PR #86339)

[via cfe-commits]

mikaelholmen wrote:

@zahiraam I still get
```
../../clang/unittests/AST/DeclPrinterTest.cpp:1394:3: error: expression result unused [-Werror,-Wunused-value]
  [](PrintingPolicy &Policy) { Policy.SuppressTagKeyword = false; };
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../clang/unittests/AST/DeclPrinterTest.cpp:1405:3: error: expression result unused [-Werror,-Wunused-value]
  [](PrintingPolicy &Policy) { Policy.SuppressTagKeyword = false; };
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../clang/unittests/AST/DeclPrinterTest.cpp:1416:3: error: expression result unused [-Werror,-Wunused-value]
  [](PrintingPolicy &Policy) { Policy.SuppressTagKeyword = true; };
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../clang/unittests/AST/DeclPrinterTest.cpp:1435:3: error: expression result unused [-Werror,-Wunused-value]
  [](PrintingPolicy &Policy) { Policy.SuppressTagKeyword = false; };
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../clang/unittests/AST/DeclPrinterTest.cpp:1455:3: error: expression result unused [-Werror,-Wunused-value]
  [](PrintingPolicy &Policy) { Policy.SuppressTagKeyword = true; };
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
5 errors generated.
```
This has been broken for quite a while now, can you please fix or revert?

https://github.com/llvm/llvm-project/pull/86339