add release-1.6 branch to the github workflows

[nawazkh]

What this PR does / why we need it:
This PR updates github workflows to include release-1.6 branch and drops release-1.4 branch

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes # N/A

[k8s-ci-robot]

This PR is currently missing an area label, which is used to identify the modified component when generating release notes.

Area labels can be added by org members by writing /area ${COMPONENT} in a comment

Please see the labels list for possible areas.

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[nawazkh]

Hold until release-1.6 branch exists.
/hold

[nawazkh]

For continuity of context, if a reviewer is approving this PR, please also take a look at kubernetes/test-infra#31208

[sbueringer]

/lgtm
/approve

(+/- pr tiltle / area)

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 47e52faa814752483e2777a6a64ef041294a7d35

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sbueringer

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[nawazkh]

(+/- pr tiltle / area)

I can update this, not sure which area this PR belongs to?
And by "title", shall I be updating the title to something else?

[nawazkh]

Looks like #9708 has already been merged achieving the same.
/close

[k8s-ci-robot]

@nawazkh: Closed this PR.

In response to this:

Looks like #9708 has already been merged achieving the same.
/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[sbueringer]

Please try to avoid duplicate PRs in the future, I think we had a similar duplicate one in test-infra :)

[sbueringer]

I can update this, not sure which area this PR belongs to? And by "title", shall I be updating the title to something else?

I guess area/release or something :), Without an icon as a prefix the GitHub check won't succeed in general