formula_auditor: also use tag when checking GitHub license

[cho-m]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

Also check tag info to work when URL is a git tag, e.g. current influxdb

❯ git checkout -q master

❯ brew audit --online --git --only license influxdb; echo $?
influxdb
  * Formula license ["MIT"] does not match GitHub license ["Apache-2.0"].
Error: 1 problem in 1 formula detected.
1

❯ git checkout -q formula_auditor-also-check-tag

❯ brew audit --online --git --only license influxdb; echo $?
0

❯ gh api 'repos/influxdata/influxdb/license?ref=v2.7.5' | jq .license
{
  "key": "mit",
  "name": "MIT License",
  "spdx_id": "MIT",
  "url": "https://api.github.com/licenses/mit",
  "node_id": "MDc6TGljZW5zZTEz"
}

[MikeMcQuaid]

Makes sense to me, thanks @cho-m!