Use release drafter v7 (#234)

Explicitly load release drafter base config from GitHub

Release drafter v7 no longer accepts .github as a valid extension.

The release drafter documentation (https://github.com/release-drafter/release-drafter/blob/master/docs/configuration-loading.md#fetching-from-a-repo-named-github) says

  The github: prefix is used internally to recognize you want to
  explicitly fetch from a remote (using octokit) instead of loading a file
  on the runtime's filesystem.

Author: MarkEWaite

.github/release-drafter.yml

@@ -1,4 +1,4 @@
 # https://github.com/jenkinsci/.github/blob/master/.github/release-drafter.adoc
 
-_extends: .github
+_extends: github:jenkinsci/.github:/.github/release-drafter.yml
 tag-template: http_request-$NEXT_MINOR_VERSION

.github/workflows/release-drafter.yml

@@ -11,6 +11,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       # Drafts your next Release notes as Pull Requests are merged into the default branch
-      - uses: release-drafter/release-drafter@v6
+      - uses: release-drafter/release-drafter@v7
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}