Use COINBASE_MATURITY constant in functional tests.

test/functional/wallet_balance.py

@@ -7,6 +7,7 @@ from decimal import Decimal
 import struct
 
 from test_framework.address import ADDRESS_BCRT1_UNSPENDABLE as ADDRESS_WATCHONLY
+from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -72,7 +73,7 @@ class WalletTest(BitcoinTestFramework):
         self.nodes[0].generate(1)
         self.sync_all()
         self.nodes[1].generate(1)
-        self.nodes[1].generatetoaddress(101, ADDRESS_WATCHONLY)
+        self.nodes[1].generatetoaddress(COINBASE_MATURITY + 1, ADDRESS_WATCHONLY)
         self.sync_all()
 
         if not self.options.descriptors: