fix(workflows): don't run metric collector on forks

[LukoJy3D]

What this PR does / why we need it:

After a recent fork sync metrics-collector action started spamming with unsuccessful runs, but since its only used for github issue triage in the playground, there is no need for it to run on forks?

Run ./actions/metrics-collector
/home/runner/work/loki/loki/actions/node_modules/@actions/core/lib/core.js:106
        throw new Error(`Input required and not supplied: ${name}`);
        ^

Error: Input required and not supplied: token
    at Object.getInput (/home/runner/work/loki/loki/actions/node_modules/@actions/core/lib/core.js:106:15)
    at getRequiredInput (/home/runner/work/loki/loki/actions/common/utils.js:40:41)
    at new ActionBase (/home/runner/work/loki/loki/actions/common/Action.js:16:51)
    at new Action (/home/runner/work/loki/loki/actions/common/Action.js:103:9)
    at new MetricsCollector (/home/runner/work/loki/loki/actions/metrics-collector/index.js:8:9)
    at Object.<anonymous> (/home/runner/work/loki/loki/actions/metrics-collector/index.js:56:1)
    at Module._compile (node:internal/modules/cjs/loader:1198:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1252:10)
    at Module.load (node:internal/modules/cjs/loader:1076:32)
    at Function.Module._load (node:internal/modules/cjs/loader:911:12)

Since there were no changes in action itself I assume something changed with repo action settings

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[cstyan]

yep this seems like an action that should only run on our own upstream repo 👍