Tweak the first-interaction workflow (#7134)

* Fix wrong YAML multiline string format

The `|` causes strings to retain newlines, which is a problem in
GitHub-flavored Markdown because GitHub retains the line breaks.

* Don't welcome Dependabot

On new repos where Dependabot hasn't run yet, the workflow would
needlessly greet Dependabot's first interaction. This now makes it
check and not run if Dependabot is the actor.

Author: mhucka

.github/workflows/first-interaction.yaml

@@ -17,6 +17,7 @@ permissions: read-all
 
 jobs:
   welcome:
+    if: github.actor != 'dependabot[bot]'
     name: Check for first interaction
     runs-on: ubuntu-24.04
     timeout-minutes: 10
@@ -31,7 +32,7 @@ jobs:
         uses: actions/first-interaction@d94ed8e502bc16de558688b9dd9a26261ae78a66 # v1.3.0
         with:
           repo-token: ${{secrets.GITHUB_TOKEN}}
-          issue-message: |
+          issue-message: >
             Hello and welcome, ${{github.actor}} 👋!
 
             Thanks for filing your first issue with the ${{github.repository}}
@@ -52,7 +53,7 @@ jobs:
             any that look the same as this one. If you find a similar issue,
             consider closing this one; if you don't want to close this one, can
             you explain how this new one differs from the other one?
-          pr-message: |
+          pr-message: >
             Hello and welcome, ${{github.actor}} 👋!
 
             Thanks for making your first pull request to the