rename:rebuild_cache function to cache

This change updates the function name for clarity and brevity. The corresponding import statement and function call in `tasks.py` were also updated to reflect this new name.

orp/orp_search/cache/rebuild.py

@@ -10,7 +10,7 @@
 logger = logging.getLogger(__name__)
 
 
-def rebuild_cache():
+def cache():
     """
     Rebuilds cache for Legislation and PublicGateway.
 

orp/orp_search/cache/tasks.py

@@ -1,7 +1,7 @@
 from celery import shared_task
-from orp_search.cache.rebuild import rebuild_cache
+from orp_search.cache.rebuild import cache
 
 
 @shared_task
 def rebuild_cache_task():
-    return rebuild_cache()
+    return cache()