fix(docs): add kubectl to retina commands

[kamilprz]

Description

Update documentation to include kubectl prefix in the commands to remain consistent with the rest of the page.

Related Issue

#733

Checklist

• I have read the contributing documentation.
• I signed and signed-off the commits (git commit -S -s ...). See this documentation on signing commits.
• I have correctly attributed the author(s) of the code.
• I have tested the changes locally.
• I have followed the project's style guidelines.
• I have updated the documentation, if necessary.
• I have added tests, if applicable.

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[kamilprz]

The force pushes above were to fix my mistake of pushing an unsigned commit :) Can be ignored.