chore: fix codecov path

[mayurkale22]

Which problem is this PR solving?

• Move codecov report inside the packages folder. Earlier: https://codecov.io/gh/open-telemetry/opentelemetry-js/tree/39732fabe85b1bca064b91c3d84a101998e71d1b, Now: https://codecov.io/gh/open-telemetry/opentelemetry-js/pull/520/tree/packages

[codecov-io]

Codecov Report

Merging #520 into master will increase coverage by 3.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #520      +/-   ##
==========================================
+ Coverage    86.6%   89.73%   +3.12%     
==========================================
  Files         131      131              
  Lines        6646     6703      +57     
  Branches      613      611       -2     
==========================================
+ Hits         5756     6015     +259     
+ Misses        890      688     -202

Impacted Files	Coverage Δ
...kages/opentelemetry-metrics/test/mocks/Exporter.ts	66.66% <0%> (-33.34%)	⬇️
...ges/opentelemetry-core/src/common/ConsoleLogger.ts	91.66% <0%> (-2.46%)	⬇️
...core/src/context/propagation/BinaryTraceContext.ts	96.72% <0%> (-1.32%)	⬇️
...telemetry-core/src/context/propagation/B3Format.ts	96% <0%> (-1.15%)	⬇️
...core/src/context/propagation/NoopHttpTextFormat.ts	100% <0%> (ø)	⬆️
.../opentelemetry-core/src/trace/spancontext-utils.ts	100% <0%> (ø)	⬆️
...ages/opentelemetry-core/src/internal/validators.ts	100% <0%> (ø)	⬆️
...opentelemetry-core/src/trace/globaltracer-utils.ts	100% <0%> (ø)	⬆️
...ckages/opentelemetry-exporter-zipkin/src/zipkin.ts
...-plugin-postgres/opentelemetry-plugin-pg/src/pg.ts
... and 50 more

[mayurkale22]

/cc @xiao-lix