Docs: fixed behavior of OVERRIDE_RELEASE_MIGRATION_OVERWRITE env var

[AlbertoPimpo]

There is a mistake in the README regarding the behavior of the environment variable OVERRIDE_RELEASE_MIGRATION_OVERWRITE .

The correct behavior, as shown here is that the override is triggered if the env var is not set or if it is different than false.

This MR clarifies this in the README.

[openshift-ci[bot]]

Hi @AlbertoPimpo. Thanks for your PR.

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[coreydaley]

/test all

[coreydaley]

/lgtm

[coreydaley]

/approve

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AlbertoPimpo, coreydaley

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/openshift/jenkins/blob/master/OWNERS)~~ [coreydaley] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AlbertoPimpo, coreydaley

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/openshift/jenkins/blob/master/OWNERS)~~ [coreydaley] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[coreydaley]

/label px-approved /label docs-approved /label qe-approved

[openshift-ci[bot]]

@AlbertoPimpo: all tests passed!

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