kernel/svc: Correct misleading error message within CreateThread()

This is a bounds check to ensure that the thread priority is within the
valid range of 0-64. If it exceeds 64, that doesn't necessarily mean
that an actual priority of 64 was expected (it actually means whoever
called the function screwed up their math).

Instead clarify the message to indicate the allowed range of thread
priorities.

src/core/hle/kernel/svc.cpp

@@ -1239,8 +1239,9 @@ static ResultCode CreateThread(Handle* out_handle, VAddr entry_point, u64 arg, V
     }
 
     if (priority > THREADPRIO_LOWEST) {
-        LOG_ERROR(Kernel_SVC, "An invalid priority was specified, expected {} but got {}",
-                  THREADPRIO_LOWEST, priority);
+        LOG_ERROR(Kernel_SVC,
+                  "Invalid thread priority specified ({}). Must be within the range 0-64",
+                  priority);
         return ERR_INVALID_THREAD_PRIORITY;
     }