added Gemini Suggestion

Author: JesusRojass

FirebasePerformance/Sources/AppActivity/FPRTraceBackgroundActivityTracker.m

@@ -23,6 +23,8 @@ @interface FPRTraceBackgroundActivityTracker ()
 
 @property(nonatomic, readwrite) FPRTraceState traceBackgroundState;
 
+- (void)registerNotificationObservers;
+
 @end
 
 @implementation FPRTraceBackgroundActivityTracker