[clang] [NFC][Clang][Preprocessor] Refine the implementation of isNextPPTokenOneOf (PR #145546)

[Erich Keane via cfe-commits]

================
@@ -2304,7 +2304,8 @@ class Preprocessor {
 
   /// Check whether the next pp-token is one of the specificed token kind. this
   /// method should have no observable side-effect on the lexed tokens.
-  template <tok::TokenKind K, tok::TokenKind... Ks> bool isNextPPTokenOneOf() {
+  template <typename... Ts>
+  bool isNextPPTokenOneOf(tok::TokenKind K, Ts... Ks) {
----------------
erichkeane wrote:

Could we make it:

```suggestion
  bool isNextPPTokenOneOf(Ts... Ks) {
```

?

Though I guess an empty pack here ends up going through all of the other work, which is... awkward.  But a `static_assert(sizeof(Ks) > 0)` accomplishes that too?  

IDK, something to think about.

https://github.com/llvm/llvm-project/pull/145546