[build] fix error in github release step (#6349)
[build] fix error in github release step (#6349)

The github release step in `publish-stable` was failing because it was trying to copy the output files from a directory it was already in. Adding a `cd ../` to fix this.

Fixes #6337
open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector-contrib