check-commit: omit whitespace

This is fixing for 'no whitespace around = for named parameters'
check-code rule.

check-code has overlooked this, because a file isn't recognized as one
to be checked (this problem is fixed by subsequent patch).

contrib/check-commit

@@ -46,7 +46,7 b' def nonempty(first, second):'
         return first
     return second
 
-def checkcommit(commit, node = None):
+def checkcommit(commit, node=None):
     exitcode = 0
     printed = node is None
     hits = []