Fixing unused variables failure in windows for clang 17

Summary:
Sometimes variables are declared, but go unused. Some LLVM versions allow this, while others (newer versions) result in errors

This diff: Removes the unused variable `policy` in the function signatures as they result in errors when compiled using clang 17

#buildall

Reviewed By: jdonald

Differential Revision: D70846863

fbshipit-source-id: 377d91043cb25b1a954bb2e81a265d709b212171

Author: Uche Uba

folly/portability/Sched.cpp

@@ -28,11 +28,11 @@ int sched_yield() {
 }
 
 // There is only 1 scheduling policy on Windows
-int sched_get_priority_min(int policy) {
+int sched_get_priority_min(int) {
   return -15;
 }
 
-int sched_get_priority_max(int policy) {
+int sched_get_priority_max(int) {
   return 15;
 }
 } // namespace sched