[DPC-3596] Fix workflow logic (#121)

## 🎫 Ticket

https://jira.cms.gov/browse/3596

## 🛠 Changes

Previous workflow sent a Slack message regardless of whether the test
succeeded or not. Now it only sends on failures.

## ℹ️ Context

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non-technical audience. -->

<!-- If any of the following security implications apply, this PR must
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and add @SJWalter11 as a reviewer.
  - Adds a new software dependency or dependencies.
  - Modifies or invalidates one or more of our security controls.
  - Stores or transmits data that was not stored or transmitted before.
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## 🧪 Validation

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criteria in the ticket? Provide reproducible testing instructions and
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.github/workflows/broken-link-check.yml

@@ -15,11 +15,10 @@ jobs:
         uses: lycheeverse/lychee-action@v1
         id: lychee
         with:
-          fail: true
           jobSummary: true
           args: --no-progress --accept '200..=299, 401, 405' .
-      - name: "Send Slack alert if failing"
-        if: always() && env.lychee_exit_code != 0
+      - name: "Send Slack alert"
+        if: env.lychee_exit_code != 0
         uses: slackapi/[email protected]
         env:
           SLACK_WEBHOOK_URL: "https://hooks.slack.com/triggers/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" # TODO: set as env var?
@@ -28,3 +27,6 @@ jobs:
             {
               "Details": "${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
             }
+      - name: "Fail workflow"
+        if: env.lychee_exit_code != 0
+        run: exit ${{ env.lychee_exit_code }}