[ios] Tidy up of iOS imports and other misc clean up

ios/RNFirebase/RNFirebase.m

@@ -1,36 +1,18 @@
 #import "RNFirebase.h"
-#import "RNFirebaseEvents.h"
-
-static dispatch_once_t onceToken;
 
 @implementation RNFirebase
 RCT_EXPORT_MODULE(RNFirebase);
 
-
-- (void)dealloc {
-    NSLog(@"Dealloc called on RNFirebase: %@", self);
-    [[NSNotificationCenter defaultCenter] removeObserver:self];
-}
-
 - (id)init {
     self = [super init];
     if (self != nil) {
         NSLog(@"Setting up RNFirebase instance");
-        [RNFirebase initializeRNFirebase];
     }
     return self;
 }
 
-+ (void)initializeRNFirebase {
-#if __has_include(<FirebaseMessaging/FirebaseMessaging.h>)
-    dispatch_once(&onceToken, ^{
-        [[NSNotificationCenter defaultCenter] postNotificationName:kRNFirebaseInitialized object:nil];
-    });
-#endif
-}
-
 - (NSArray<NSString *> *)supportedEvents {
-    return @[INITIALIZED_EVENT];
+    return @[];
 }
 
-@end
+@end