test: refactor: deduplicate DEFAULT_{ANCESTOR,DESCENDANT}_LIMIT constants

test/functional/test_framework/messages.py

@@ -65,6 +65,9 @@ FILTER_TYPE_BASIC = 0
 
 WITNESS_SCALE_FACTOR = 4
 
+DEFAULT_ANCESTOR_LIMIT = 25    # default max number of in-mempool ancestors
+DEFAULT_DESCENDANT_LIMIT = 25  # default max number of in-mempool descendants
+
 
 def sha256(s):
     return hashlib.sha256(s).digest()