cqle: remove special handling for bool in ValueQuoter

now that cql_quote does not quote bool types, this is not needed

PYTHON-596

cassandra/cqlengine/statements.py

@@ -35,9 +35,7 @@ class ValueQuoter(UnicodeMixin):
 
     def __unicode__(self):
         from cassandra.encoder import cql_quote
-        if isinstance(self.value, bool):
-            return 'true' if self.value else 'false'
-        elif isinstance(self.value, (list, tuple)):
+        if isinstance(self.value, (list, tuple)):
             return '[' + ', '.join([cql_quote(v) for v in self.value]) + ']'
         elif isinstance(self.value, dict):
             return '{' + ', '.join([cql_quote(k) + ':' + cql_quote(v) for k, v in self.value.items()]) + '}'