Revert incorrect header import path

- Fix BackgroundRefreshStrategy.m to use correct local header import
- Remove permission_handler_apple/ prefix from import statement

Author: ened

permission_handler_apple/ios/permission_handler_apple/Sources/permission_handler_apple/strategies/BackgroundRefreshStrategy.m

@@ -5,7 +5,7 @@
 //  Created by Sebastian Roth on 28/09/2023.
 //
 
-#import "permission_handler_apple/BackgroundRefreshStrategy.h"
+#import "BackgroundRefreshStrategy.h"
 
 @implementation BackgroundRefreshStrategy