Use remote schema for Prometheus rule

[hayk96]

1. What this PR does / why we need it:

• Replacing the schema validation mechanism. Since the SchemaStore has a valid schema for the Prometheus rules, this approach will allow us to have an up-to-date schema. It will eliminate the need for additional maintenance in this app to keep the Rule schema up to date

2. Make sure that you've checked the boxes below before you submit PR:

• DCO signed
• No conflict with the main branch.