Add release_build workflow to Release environment (#141)

In this PR, we are changing the release_build workflow to run in the
Release environment. The Release environment has been configured to
require approval from another member of the team for workflow runs
(called deployments), reducing the chance of accidental releases from
going out etc.

For more details, see
https://docs.github.com/en/actions/deployment/targeting-different-environments/using-environments-for-deployment

Testing: Created a dummy workflow and added to the release env, then
performed a deployment with another member of the team:
https://github.com/aws-observability/aws-otel-python-instrumentation/actions/workflows/env-test.yml

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choice.

Author: thpierce

.github/workflows/release_build.yml

@@ -21,6 +21,7 @@ permissions:
 
 jobs:
   build:
+    environment: Release
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Contrib Repo @ SHA - ${{ github.sha }}