Remove unused grantors function in MQDescriptor

We don't want to be returning a mutable reference to the grantors. Since
this function isn't being used anywhere, it is being removed.

Fixes: 162465295
Test: m && atest fmq_test
Change-Id: Ib5e519d100706c2443da99b85b27aa8dcb543d35
diff --git a/base/include/hidl/MQDescriptor.h b/base/include/hidl/MQDescriptor.h
index 786c1be..0429444 100644
--- a/base/include/hidl/MQDescriptor.h
+++ b/base/include/hidl/MQDescriptor.h
@@ -57,12 +57,6 @@
         return mGrantors;
     }
 
-    // This should be removed if no one is using it. We shouldn't be returning
-    // a mutable reference if it's not necessary. TODO(b/162465295).
-    inline ::android::hardware::hidl_vec<GrantorDescriptor> &grantors() {
-        return mGrantors;
-    }
-
     inline const ::native_handle_t *handle() const {
         return mHandle;
     }