fix: bump stale agent to 7.13-SNAPSHOT

[mdelapenya]

What does this PR do?

It uses one minor version for the stale agent

Why is it important?

For master branch, using 8.0.0-SNAPSHOT, it's incorrect to use 7.11-SNAPSHOT as stale agent, as that version has disappeared from the artifactory.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have run the Unit tests for the CLI, and they are passing locally
• I have run the End-2-End tests for the suite I'm working on, and they are passing locally
• I have noticed new Go dependencies (run make notice in the proper directory)

Author's Checklist

• @michalpristas, can you confirm that the stale version is correct for master?

Follow-ups

Thinkg about upgrade processes, what if we want to test the upgrade of an old version? Using the artifact repository won't be enough, as versions disappears after 2 minor versions of the stack.

Maybe this is something to ask infra, about allowing accessing those old versions from another repository.

[elasticmachine]

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• Build Cause: Started by user Manuel de la Peña

• Start Time: 2021-05-06T08:53:41.726+0000

• Duration: 14 min 16 sec

• Commit: fb36df1

Test stats 🧪

Test	Results
Failed	0
Passed	26
Skipped	0
Total	26

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Test stats 🧪

Test	Results
Failed	0
Passed	26
Skipped	0
Total	26

[mdelapenya]

I'm triggering the CI job running the nightly tests, as the upgrade test is run in that schedule

[michalpristas]

looks good