Add cli-discuss-automation environment to triage.md

Previously, we were getting the token from repository secrets. We have
moved the token to its own environment secret in the
cli-discuss-automation environment. It is in its own environment so that
we don't inject our other secrets into this workflow as we don't need
them here.

.github/workflows/triage.yml

@@ -11,6 +11,7 @@ env:
   TARGET_REPO: github/cli
 jobs:
   issue:
+    environment: cli-discuss-automation
     runs-on: ubuntu-latest
     if: github.event_name == 'issues' && github.event.action == 'labeled' && github.event.label.name == 'discuss'
     steps:
@@ -42,6 +43,7 @@ jobs:
 
   pull_request:
     runs-on: ubuntu-latest
+    environment: cli-discuss-automation
     if: github.event_name == 'pull_request_target' && github.event.action == 'labeled' && github.event.label.name == 'discuss'
     steps:
       - name: Create issue based on source pull request