Cleanup the Prometheus config

[FlamingSaint]

Which problem is this PR solving?

• Part of [jaeger v2] Service Performance Monitoring #5632

Description of the changes

• Cleaned up the Prometheus config
• Removed namespaceConfig as its not needed for a metrics storage

How was this change tested?

• make test

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
  - [ ] I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: yarn lint and yarn test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.87%. Comparing base (ea2ec18) to head (5903ef0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5720      +/-   ##
==========================================
- Coverage   96.89%   96.87%   -0.02%     
==========================================
  Files         334      334              
  Lines       16146    16141       -5     
==========================================
- Hits        15644    15637       -7     
- Misses        333      334       +1     
- Partials      169      170       +1     

Flag	Coverage Δ
badger_v1	8.06% <ø> (ø)
badger_v2	1.90% <ø> (ø)
cassandra-3.x-v1	16.62% <ø> (ø)
cassandra-3.x-v2	1.82% <ø> (ø)
cassandra-4.x-v1	16.62% <ø> (ø)
cassandra-4.x-v2	1.82% <ø> (ø)
elasticsearch-6.x-v1	18.80% <ø> (ø)
elasticsearch-7.x-v1	18.86% <ø> (+0.01%)	⬆️
elasticsearch-8.x-v1	19.04% <ø> (-0.02%)	⬇️
elasticsearch-8.x-v2	1.89% <ø> (-0.02%)	⬇️
grpc_v1	9.46% <ø> (ø)
grpc_v2	7.41% <ø> (ø)
kafka	9.75% <ø> (ø)
opensearch-1.x-v1	18.91% <ø> (+0.01%)	⬆️
opensearch-2.x-v1	18.90% <ø> (-0.02%)	⬇️
opensearch-2.x-v2	1.90% <ø> (ø)
unittests	95.26% <100.00%> (-0.02%)	⬇️

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