Only run scheduled jobs on bitnami/minideb repo

[jerrykan]

I'm assuming the scheduled jobs are mainly to keep the images up-to-date. For most repository forks there is no real need to run these builds on a schedule and just use up build resources necessarily.

[jerrykan]

I forgot the DCO/Signed-off-by tags in my original commits, that should be fixed in the updated commit.

[carrodher]

Thanks for creating this PR. Please, note it is needed to sign the commits. Your signature certifies that you wrote the patch or otherwise have the right to contribute the material. You can find more info about this topic, in the “Sign your work” section from the contributing guidelines.

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