Enhance FirebaseInAppMessaging unit test files (#13802)

Author: MojtabaHs

FirebaseInAppMessaging/Tests/Unit/FIRIAMMessageClientCacheTests.m

@@ -328,7 +328,7 @@ - (void)testCallingStartAnalyticsEventListenFlow_ok {
   self.clientCache.analycisEventDislayCheckFlow = mockAnalyticsEventFlow;
 
   // m2 and m4 are messages rendered on 'test_event' Firebase Analytics event
-  // so we espect the analytics event listening flow to be started
+  // so we expect the analytics event listening flow to be started
   OCMExpect([mockAnalyticsEventFlow start]);
   [self.clientCache setMessageData:@[ m1, m2, m3, m4 ]];
   OCMVerifyAll((id)mockAnalyticsEventFlow);