Use standard order of keys in "Check Certificates" workflow steps

Although machines don't care which order the keys occur in, since the `jobs[].<job_id>.steps[].env` key declares the
environment variables used in the step, it is most intuitive for it to be placed before the `run` or `uses` key.

Author: per1234

.github/workflows/check-certificates.yml

@@ -65,7 +65,6 @@ jobs:
       # See: https://github.com/rtCamp/action-slack-notify
       - name: Slack notification of certificate verification failure
         if: failure()
-        uses: rtCamp/action-slack-notify@v2
         env:
           SLACK_WEBHOOK: ${{ secrets.TEAM_TOOLING_CHANNEL_SLACK_WEBHOOK }}
           SLACK_MESSAGE: |
@@ -74,6 +73,7 @@ jobs:
             :warning::warning::warning::warning:
           SLACK_COLOR: danger
           MSG_MINIMAL: true
+        uses: rtCamp/action-slack-notify@v2
 
       - name: Get days remaining before certificate expiration date
         env:
@@ -119,7 +119,6 @@ jobs:
       - name: Slack notification of pending certificate expiration
         # Don't send spurious expiration notification if verification fails
         if: failure() && steps.check-expiration.outcome == 'failure'
-        uses: rtCamp/action-slack-notify@v2
         env:
           SLACK_WEBHOOK: ${{ secrets.TEAM_TOOLING_CHANNEL_SLACK_WEBHOOK }}
           SLACK_MESSAGE: |
@@ -128,3 +127,4 @@ jobs:
             :warning::warning::warning::warning:
           SLACK_COLOR: danger
           MSG_MINIMAL: true
+        uses: rtCamp/action-slack-notify@v2