fix: Skip releasing chart if it already exists (#1271)

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Last week, [this workflow
run](https://github.com/newrelic/helm-charts/actions/runs/7710787642/job/21014874442)
created tag `nri-bundle-5.0.61` after tag `super-agent-0.0.2-beta`, so
we know for sure temporal dependencies between the two tags.

However, this week [this workflow run
failed](https://github.com/newrelic/helm-charts/actions/runs/7799298965/job/21269820082)
because it read tag `super-agent-0.0.2-beta` as if it were the latest.

While it is not clear the source of the issue (bad cache, chart releaser
action bug?), we can use the flag `--skip-existing` to tell the chart
releaser not to fail when a release already exists, adding more
reliability to our workflow.


#### Checklist
[Place an '[x]' (no spaces) in all applicable fields. Please remove
unrelated fields.]
- [ ] Chart Version bumped
- [ ] Variables are documented in the README.md
- [ ] Title of the PR starts with chart name (e.g. `[mychartname]`)

.github/workflows/release.yml

@@ -105,6 +105,7 @@ jobs:
           # so use alternative token to allow post-release workflow to run
           # Source: https://docs.github.com/en/actions/security-guides/automatic-token-authentication#using-the-github_token-in-a-workflow
           CR_TOKEN: "${{ secrets.K8S_AGENTS_BOT_TOKEN }}"
+          CR_SKIP_EXISTING: true
 
   notify-failure:
     if: ${{ always() && failure() && (github.event_name == 'schedule') }}