pw_allocator: Remove unnecessary template

Upstreams cl/649061659. This change prevents a break from occurring when
-Wmissing-template-arg-list-after-template-kw is enabled

Change-Id: Ie1668a5199f3e48b625796f7d2f8149001dcb6bd
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/220111
Lint: Lint 🤖 <[email protected]>
Commit-Queue: Auto-Submit <[email protected]>
Pigweed-Auto-Submit: Ted Pudlik <[email protected]>
Reviewed-by: Aaron Green <[email protected]>

pw_allocator/public/pw_allocator/size_reporter.h

@@ -103,7 +103,7 @@ class SizeReporter final {
  Foo* foo = allocator.template New<Foo>();
 
  // Measure `Delete`.
- allocator.template Delete(foo);
+ allocator.Delete(foo);
 
  // Measure `MakeUnique`.
  UniquePtr<Foo> unique_foo = allocator.template MakeUnique<Foo>();