Remove duplicate keys initialDelaySeconds, timeoutSeconds

[psy-q]

Summary

This PR removes two duplicate keys from the MariaDB tutorial deployment's spec.template.spec.readinessProbe section. This way, the k8up tutorial works again as documented.

Otherwise kubectl throws an error:

error: map[string]interface {}(nil): yaml: unmarshal errors:
  line 37: mapping key "timeoutSeconds" already defined at line 27
  line 36: mapping key "initialDelaySeconds" already defined at line 28

At least when using kubectl 1.21.1 against apiserver 1.20.2. I'm not sure which part (kubectl or the API server) does these validations.

Checklist

• Keep pull requests small so they can be easily reviewed.
• Categorize the PR by setting a good title and adding one of the labels:
  bug, enhancement, documentation, change, breaking,
  as they show up in the changelog

[ccremer]

(Please label documentation fixes with documentation :) )