test: Remove wallet option from non-wallet tests

Review note: The changes are complete, because self.options.descriptors
is set to None in parse_args (test_framework.py).

A value of None implies -disablewallet, see the previous commit.

So if a call to add_wallet_options is missing, it will lead to a test
failure when the wallet is compiled in.

test/functional/feature_pruning.py

@@ -76,6 +76,9 @@ def calc_usage(blockdir):
     return sum(os.path.getsize(blockdir + f) for f in os.listdir(blockdir) if os.path.isfile(os.path.join(blockdir, f))) / (1024. * 1024.)
 
 class PruneTest(BitcoinTestFramework):
+    def add_options(self, parser):
+        self.add_wallet_options(parser)
+
     def set_test_params(self):
         self.setup_clean_chain = True
         self.num_nodes = 6