Fix missing aggregate query headers in umbrella (#10301) (#10302)

* Fix missing aggregate query headers in umbrella

* remove duplicate import in test

Co-authored-by: Morgan Chen <morganchen12@gmail.com>

Firestore/Example/Tests/Integration/API/FIRCountTests.mm

@@ -19,9 +19,6 @@
 #import <XCTest/XCTest.h>
 
 #import "Firestore/Example/Tests/Util/FSTIntegrationTestCase.h"
-#import "Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuery.h"
-#import "Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuerySnapshot.h"
-#import "Firestore/Source/Public/FirebaseFirestore/FIRAggregateSource.h"
 
 @interface FIRCountTests : FSTIntegrationTestCase
 @end

Firestore/Source/Public/FirebaseFirestore/FirebaseFirestore.h

@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+#import "FIRAggregateQuery.h"
+#import "FIRAggregateQuerySnapshot.h"
+#import "FIRAggregateSource.h"
 #import "FIRCollectionReference.h"
 #import "FIRDocumentChange.h"
 #import "FIRDocumentReference.h"