fix: add semantic commit prefix to dependabot PRs (#131)

## Which problem is this PR solving?
Our dependabot PRs are failing CI checks because of the PR title
validation check. Instead of getting the PR title validation check to
ignore dependabot PRs, I thought it would be better to add the correct
semantic prefix to dependabot PRs instead.

- Updates honeycombio/telemetry-team#389

## Short description of the changes
- Adds semantic prefix `maint` to all dependabot commits / PRs

## How to verify that this has the expected result
Unfortunately, it doesn't seem like we can validate dependabot config
changes without merging them in according to [this
issue](dependabot/dependabot-core#4605).

I think this should work as expected based on:
- [The dependabot docs for
`commit-message`](https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#commit-message)
- [The code adds a `:` and a space automatically

](https://github.com/dependabot/dependabot-core/blob/main/common/spec/dependabot/pull_request_creator/pr_name_prefixer_spec.rb#L248)

.github/dependabot.yml

@@ -13,3 +13,6 @@ updates:
       - "type: dependencies"
     reviewers:
       - "honeycombio/telemetry-team"
+    commit-message:
+      prefix: "maint"
+      include_scope: true