fix: typo in a property name

Author: MojtabaHs

FirebaseInstallations/Source/Tests/Unit/FIRInstallationsItemTests.m

@@ -68,11 +68,11 @@ - (void)testValidate_InvalidItem {
   XCTAssertTrue(
       [validationError.localizedFailureReason containsString:@"invalid `registrationStatus`"]);
 
-  FIRInstallationsItem *registerredItem = [[FIRInstallationsItem alloc] initWithAppID:@""
+  FIRInstallationsItem *registeredItem = [[FIRInstallationsItem alloc] initWithAppID:@""
                                                                       firebaseAppName:@""];
-  registerredItem.registrationStatus = FIRInstallationStatusRegistered;
+  registeredItem.registrationStatus = FIRInstallationStatusRegistered;
 
-  XCTAssertFalse([registerredItem isValid:&validationError]);
+  XCTAssertFalse([registeredItem isValid:&validationError]);
   XCTAssertTrue(
       [validationError.localizedFailureReason containsString:@"`appID` must not be empty"]);
   XCTAssertTrue([validationError.localizedFailureReason