AnyInvocable: Fix operator==/!= comments

Comments referred to `*this` instead of `f`.

#Cleanup
#Documentation

PiperOrigin-RevId: 775664647
Change-Id: Ibdd9a1611d59078a1b368985c8929154faef527a
diff --git a/absl/functional/any_invocable.h b/absl/functional/any_invocable.h
index 43ea9af..524345d 100644
--- a/absl/functional/any_invocable.h
+++ b/absl/functional/any_invocable.h
@@ -295,22 +295,22 @@
 
   // Equality operators
 
-  // Returns `true` if `*this` is empty.
+  // Returns `true` if `f` is empty.
   friend bool operator==(const AnyInvocable& f, std::nullptr_t) noexcept {
     return !f.HasValue();
   }
 
-  // Returns `true` if `*this` is empty.
+  // Returns `true` if `f` is empty.
   friend bool operator==(std::nullptr_t, const AnyInvocable& f) noexcept {
     return !f.HasValue();
   }
 
-  // Returns `false` if `*this` is empty.
+  // Returns `false` if `f` is empty.
   friend bool operator!=(const AnyInvocable& f, std::nullptr_t) noexcept {
     return f.HasValue();
   }
 
-  // Returns `false` if `*this` is empty.
+  // Returns `false` if `f` is empty.
   friend bool operator!=(std::nullptr_t, const AnyInvocable& f) noexcept {
     return f.HasValue();
   }