Fix pod spec lint and remove extraneous IID refs (#7835)

Author: paulb777

FirebaseMessaging.podspec

@@ -39,8 +39,6 @@ device, and it is completely free.
     'Interop/Analytics/Public/*.h',
     'FirebaseCore/Sources/Private/*.h',
     'FirebaseInstallations/Source/Library/Private/*.h',
-    'Firebase/InstanceID/Private/*.h',
-    'Firebase/InstanceID/Public/*.h',
   ]
   s.public_header_files = base_dir + 'Sources/Public/FirebaseMessaging/*.h'
   s.library = 'sqlite3'

FirebaseMessaging/Sources/FIRMessaging.m

@@ -24,9 +24,8 @@
 #import <GoogleUtilities/GULAppEnvironmentUtil.h>
 #import <GoogleUtilities/GULReachabilityChecker.h>
 #import <GoogleUtilities/GULUserDefaults.h>
-#import "Firebase/InstanceID/Private/FIRInstanceID_Private.h"
 #import "FirebaseCore/Sources/Private/FirebaseCoreInternal.h"
-#import "FirebaseInstallations/Source/Library/Public/FirebaseInstallations/FirebaseInstallations.h"
+#import "FirebaseInstallations/Source/Library/Private/FirebaseInstallationsInternal.h"
 #import "FirebaseMessaging/Sources/FIRMessagingAnalytics.h"
 #import "FirebaseMessaging/Sources/FIRMessagingCode.h"
 #import "FirebaseMessaging/Sources/FIRMessagingConstants.h"

FirebaseMessaging/Tests/UnitTests/FIRMessagingPendingTopicsListTest.m

@@ -113,12 +113,14 @@ - (void)testBatchSizeReductionAfterSuccessfulTopicUpdate {
   XCTestExpectation *batchSizeReductionExpectation =
       [self expectationWithDescription:@"Batch size was reduced after topic suscription"];
 
+  __weak id weakSelf = self;
   self.alwaysReadyDelegate.subscriptionHandler =
       ^(NSString *topic, FIRMessagingTopicAction action,
         FIRMessagingTopicOperationCompletion completion) {
         // Simulate that the handler is generally called asynchronously
         dispatch_async(dispatch_get_main_queue(), ^{
           if (action == FIRMessagingTopicActionUnsubscribe) {
+            __unused id self = weakSelf;  // In Xcode 11, XCTAssertEqual references self.
             XCTAssertEqual(pendingTopics.numberOfBatches, 1);
             [batchSizeReductionExpectation fulfill];
           }