Fix return type hint for set_cmab_custom_cache method to improve type safety

Author: FarhanAnjum-opti

optimizely/optimizely_factory.py

@@ -118,7 +118,7 @@ def set_cmab_cache_ttl(cache_ttl: int, logger: Optional[optimizely_logger.Logger
         return OptimizelyFactory.cmab_cache_ttl
 
     @staticmethod
-    def set_cmab_custom_cache(custom_cache: LRUCache[str, CmabCacheValue]) -> LRUCache:
+    def set_cmab_custom_cache(custom_cache: LRUCache[str, CmabCacheValue]) -> LRUCache[str, CmabCacheValue]:
         """ Convenience method for setting custom CMAB cache.
         Args:
           custom_cache: Cache implementation with lookup, save, remove, and reset methods.