[6.13.z] - remove g-chat notification for failed auto-cherrypick, handled in slack

[omkarkhatavkar]

Description of changes

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Upstream API documentation, plugin, or feature links

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Functional demonstration

Provide an execution of the modified code, with ipython code blocks or screen shots.
You can exercise the code as raw API calls or using any other method.

Your contribution should include updates to the unit tests, covering the modified portions or adding new coverage.

Example:

# Demonstrate functional Snapshot read in ipython
In [1]: from nailgun.entities import Snapshot
In [2]: Snapshot(host='sat.instance.addr.com', id='snap_uuid').read()
Out [2]: <read method result>

Additional Information

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (6.13.z@fd48ffe). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff            @@
##             6.13.z     #956   +/-   ##
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  Coverage          ?   92.06%           
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  Files             ?        6           
  Lines             ?     3024           
  Branches          ?        0           
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  Hits              ?     2784           
  Misses            ?      240           
  Partials          ?        0           

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