Make unused release_namespace parameter as optional (#358)

plugins/modules/helm_plugin.py

@@ -19,10 +19,10 @@ requirements:
 description:
   -  Manages Helm plugins.
 options:
+  # TODO: (akasurde) Remove this in version 2.0
   release_namespace:
     description:
       - Kubernetes namespace where the helm plugin should be installed.
-    required: true
     type: str
     aliases: [ namespace ]
 
@@ -103,7 +103,7 @@ def main():
     module = AnsibleModule(
         argument_spec=dict(
             binary_path=dict(type='path'),
-            release_namespace=dict(type='str', required=True, aliases=['namespace']),
+            release_namespace=dict(type='str', aliases=['namespace']),
             state=dict(type='str', default='present', choices=['present', 'absent']),
             plugin_path=dict(type='str',),
             plugin_name=dict(type='str',),