Updating PR Guidelines (#413)
Updating PR Guidelines (#413)

* update pr merge guideline

* Update CONTRIBUTING.md

Co-authored-by: Tom Tan <5fc2d3cc368cf8e094b2bc925e7da57940ba5bc9@microsoft.com>

* reword, and add PR from approvers

* cosmetic

Co-authored-by: Tom Tan <5fc2d3cc368cf8e094b2bc925e7da57940ba5bc9@microsoft.com>
open-telemetry/opentelemetry-cpp,open-telemetry/opentelemetry-cpp,open-telemetry/opentelemetry-cpp,open-telemetry/opentelemetry-cpp