How to write a Custom Action in mistral

[hyunsik Yang]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [ ] This doc is inaccurate in this way: ______
- [ ] This is a doc addition request.
- [x] I have a fix to the document that I can paste below including example: input and output.

In this doc, explanation of def run is wrong.

    def run(self):
        # return your results here
        return {'status': 0}

It should be fixed like below.

    def run(self,action_ctx=None):
        # return your results here
        return {'status': 0}

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-----------------------------------
Release: on 2020-01-16 19:09:36
SHA: 545a34c7511b6e6b5f1b59ca99891684303b4480
Source: https://opendev.org/openstack/mistral/src/doc/source/developer/extensions/creating_custom_action.rst
URL: https://docs.openstack.org/mistral/latest/developer/extensions/creating_custom_action.html

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.opendev.org/722225

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/722225
Committed: https://git.openstack.org/cgit/openstack/mistral/commit/?id=d33313f84e4a77433ee5d3a3ef35f3440f7c34bd
Submitter: Zuul
Branch: master

commit d33313f84e4a77433ee5d3a3ef35f3440f7c34bd
Author: hyunsikYang <email address hidden>
Date: Thu Apr 23 08:06:11 2020 +0000

    typo of guide 'How to write a Custom Action in mistral'

    Change-Id: I48f36ad4ed2decc872e7a5ab2e086283d504da89
    Related-Bug: #1874391