chore(plugin-pg-pool): fix codecov path

[mayurkale22]

Which problem is this PR solving?

Currently, pg-pool plugin codecov report floating outside packages/ folder, see below image. Ideally, it should stay inside a packages/ folder similar to other modules.

/cc @xiao-lix

[codecov-io]

Codecov Report

Merging #657 into master will decrease coverage by 1.84%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #657      +/-   ##
==========================================
- Coverage   91.46%   89.62%   -1.85%     
==========================================
  Files         214      214              
  Lines       10043    10039       -4     
  Branches      913      931      +18     
==========================================
- Hits         9186     8997     -189     
- Misses        857     1042     +185

Impacted Files	Coverage Δ
packages/opentelemetry-core/test/utils/url.test.ts	50% <0%> (-50%)	⬇️
...pentelemetry-core/test/internal/validators.test.ts	50% <0%> (-50%)	⬇️
...elemetry-core/test/trace/spancontext-utils.test.ts	55.55% <0%> (-44.45%)	⬇️
...lemetry-core/test/trace/ProbabilitySampler.test.ts	56.52% <0%> (-43.48%)	⬇️
...s/opentelemetry-core/test/trace/NoopTracer.test.ts	60% <0%> (-40%)	⬇️
...s/opentelemetry-core/test/context/B3Format.test.ts	63.39% <0%> (-36.61%)	⬇️
...ges/opentelemetry-core/test/trace/NoopSpan.test.ts	63.63% <0%> (-36.37%)	⬇️
...s/opentelemetry-core/test/trace/tracestate.test.ts	65.06% <0%> (-34.94%)	⬇️
...kages/opentelemetry-metrics/test/mocks/Exporter.ts	66.66% <0%> (-33.34%)	⬇️
...ntelemetry-core/test/trace/NoRecordingSpan.test.ts	71.42% <0%> (-28.58%)	⬇️
... and 61 more