Remove dummy constraint from PIP

plugins/_module/pip_update.py

@@ -15,7 +15,6 @@ def main():
         supports_check_mode=False
     )
     constraints = {
-        'dummy': 'v.e.r',
         'docutils': '0.15.2',# botocore requires <16
         'chardet': '3.0.4',# Certbot fails with 4.0.0
         'idna': '2.10',# Certbot fails with 3.0