options: handle wumbo and large-channels aliases properly.

Too trivial a fix to really list in Changelog, but I noticed that we
specified "wumbo" twice.  We should really just use the proper name
in listconfigs.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_misc.py

@@ -807,6 +807,10 @@ def test_listconfigs(node_factory, bitcoind, chainparams):
     assert configs['ignore-fee-limits'] is False
     assert configs['log-prefix'] == 'lightning1-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...'
 
+    # These are aliases, but we don't print the (unofficial!) wumbo.
+    assert 'wumbo' not in configs
+    assert configs['large-channels'] is False
+
     # Test one at a time.
     for c in configs.keys():
         if c.startswith('#') or c.startswith('plugins') or c == 'important-plugins':