[bitnami/kube-prometheus] Enable PodDisruptionBudgets (part 2)

[fmulero]

Description of the change

Enabled PodDisruptionBudget by default. In previous #26553 PR, PDBs were not enabled by default.

Benefits

PDB protects our applications from voluntary disruption initiated by cluster administrators.
Keep our charts up to date according to our templates.

Possible drawbacks

None

Aditional information

• Follow up: [bitnami/kube-prometheus] Add imagePullPolicy to Prometheus and Alertmanager #26553
• Pod disruption budgets
• Specifying a Disruption Budget for your Application

Checklist

• Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• Variables are documented in the values.yaml and added to the README.md using readme-generator-for-helm
• Title of the pull request follows this pattern [bitnami/<name_of_the_chart>] Descriptive title
• All commits signed off and in agreement of Developer Certificate of Origin (DCO)

[rafariossaa]

LGTM