[prometheus-pgbouncer-exporter] remove bitnami deps and simplify CI deps

[DrFaust92]

What this PR does / why we need it

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

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Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[zeritti]

The other thing with respect to Bitnami's images in this chart is the postgresql subchart (dependency) and the corresponding image which this PR does not address.

My suggestion would be to remove the dependency and the extra container from the CI configuration entirely. This would cause no problems in CI as PgBouncer exporter does not require PgBouncer to start successfully. In fact, the CI jobs do not validate nor test whether the exporter functions as expected - launching the target service in CI seems in this sense and in this case unnecessary.

[DrFaust92]

zeritti let me try and if so ill take a look doing it more globally with other such deps (kafka, etc)

[DrFaust92]

Thanks @zeritti should be even cleaner now

[zeritti]

PgBouncer does not start without a PostgreSQL instance to connect to leading to a failure in the CI test case. I have therefore removed the extra container hoping it is ok with you, @DrFaust92. Cheers!