chore: [REL-4161] run homebrew deploy key through toJSON (#552)

Deploy keys are apparently multi-line and need to be run through toJSON
for proper encoding.
<!-- ld-jira-link -->
---
Related Jira issue: [REL-4161: Migrate ld-find-code-refs from Releaser
to GHA](https://launchdarkly.atlassian.net/browse/REL-4161)
<!-- end-ld-jira-link -->

Author: blaqbern

.github/workflows/release.yml

@@ -27,7 +27,7 @@ jobs:
       DRY_RUN: ${{ inputs.dryRun || 'false' }}
       CHANGELOG_ENTRY: ${{ inputs.changeLog }}
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      HOMEBREW_GH_TOKEN: ${{ secrets.LAUNCHDARKLY_HOMEBREW_TAP_DEPLOY_KEY }}
+      HOMEBREW_GH_TOKEN: ${{ toJSON(secrets.LAUNCHDARKLY_HOMEBREW_TAP_DEPLOY_KEY) }}
       ARTIFACT_DIRECTORY: "/tmp/release-artifacts"
     steps:
       - uses: actions/checkout@v4