ci: remove first-time contributor job in workflow and update Jenkins badges

  - Remove the automated welcome message for first-time contributors.
    Contributor related information will be maintained in project
    announcements instead, avoiding additional bot activity on PRs.
  - Update badge links for the Jenkins image builder jobs.
Signed-off-by: Shubhika Garg <shubhika.garg@openairinterface.org>

.github/workflows/jenkins-dispatch.yml

@@ -105,20 +105,3 @@ jobs:
         run: gh pr edit ${{ github.event.pull_request.number }} --remove-label "${{ vars.RETRIGGER_CI_LABEL }}"
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-  welcome-first-time-contributor:
-    runs-on: ubuntu-24.04
-    if: github.event_name == 'pull_request_target' && github.event.action == 'opened'
-
-    steps:
-      - name: Post welcome message
-        uses: actions/first-interaction@v1
-        with:
-          repo-token: ${{ secrets.GITHUB_TOKEN }}
-          pr-message: |
-            Welcome @${{ github.event.pull_request.user.login }}! Thanks for opening your first PR in this project!
-
-            Here are a few things to help you get started:
-            - Read the [Contributing Guide](https://github.com/${{ github.repository }}/blob/develop/CONTRIBUTING.md) to understand our development process.
-            - Check the [issues page](https://github.com/duranta-project/openairinterface5g/issues) to see if your PR is related to an existing issue.
-            - Add a [label](https://github.com/duranta-project/openairinterface5g/labels/) to categorize your PR so reviewers can triage it faster.

README.md

@@ -14,8 +14,8 @@
 </p>
 
 <p align="center">
-    <a href="https://jenkins-oai.eurecom.fr/job/RAN-Ubuntu18-Image-Builder/"><img src="https://img.shields.io/jenkins/build?jobUrl=https%3A%2F%2Fjenkins-oai.eurecom.fr%2Fjob%2FRAN-Ubuntu18-Image-Builder%2F&label=build-Ubuntu-x86%20Images"></a>
-    <a href="https://jenkins-oai.eurecom.fr/job/RAN-RHEL8-Cluster-Image-Builder/"><img src="https://img.shields.io/jenkins/build?jobUrl=https%3A%2F%2Fjenkins-oai.eurecom.fr%2Fjob%2FRAN-RHEL8-Cluster-Image-Builder%2F&label=build-UBI-x86%20Images"></a>
+    <a href="https://jenkins-oai.eurecom.fr/job/RAN-Ubuntu-Image-Builder/"><img src="https://img.shields.io/jenkins/build?jobUrl=https%3A%2F%2Fjenkins-oai.eurecom.fr%2Fjob%2FRAN-Ubuntu-Image-Builder%2F&label=build-Ubuntu-x86%20Images"></a>
+    <a href="https://jenkins-oai.eurecom.fr/job/RAN-RHEL-Cluster-Image-Builder/"><img src="https://img.shields.io/jenkins/build?jobUrl=https%3A%2F%2Fjenkins-oai.eurecom.fr%2Fjob%2FRAN-RHEL-Cluster-Image-Builder%2F&label=build-RHEL-Cluster%20Images"></a>
     <a href="https://jenkins-oai.eurecom.fr/job/RAN-Ubuntu-ARM-Image-Builder/"><img src="https://img.shields.io/jenkins/build?jobUrl=https%3A%2F%2Fjenkins-oai.eurecom.fr%2Fjob%2FRAN-Ubuntu-ARM-Image-Builder%2F&label=build-Ubuntu-ARM%20Images"></a>
 </p>