Fix getTestCaseCustomFieldValue "version" parameter type
Fix getTestCaseCustomFieldValue "version" parameter type

Error message details {'message': 'Parameter (version) must be an integer (current value: 1).', 'code': 210}

Tested on TestLink 1.9

savagecm/TestLink-API-Python-client,Brian-Williams/TestLink-API-Python-client,orenault/TestLink-API-Python-client,savagecm/TestLink-API-Python-client