reader/wgsl: Replace std::result_of with std::invoke_result

With C++17, std::result_of has been deprecated and superceeded with std::invoke_result.
std::result_of triggers a compiler warning about use of a deprecated feature, which is causing the ossfuzz builds to fail

Issue: oss-fuzz:43441
Change-Id: Ie4ed670dd5b25b9059d5feb8056e37a22dad3cbf
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/75981
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/reader/wgsl/parser_impl.h

@@ -695,7 +695,7 @@ class ParserImpl {
  private:
   /// ReturnType resolves to the return type for the function or lambda F.
   template <typename F>
-  using ReturnType = typename std::result_of<F()>::type;
+  using ReturnType = typename std::invoke_result<F>::type;
 
   /// ResultType resolves to `T` for a `RESULT` of type Expect<T>.
   template <typename RESULT>