tests: Increase wallet_miniscript.py rpc timeout to 90 seconds

The signing test for the large miniscript can sometimes take longer than
the 30 second timeout, depending on the load on my system. Increasing it
to 90 seconds seems to be good enough.

test/functional/wallet_miniscript.py

@@ -208,6 +208,7 @@ class WalletMiniscriptTest(BitcoinTestFramework):
 
     def set_test_params(self):
         self.num_nodes = 1
+        self.rpc_timeout = 180
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()