Bumping jenkins version to 2.303.3

Removing check-for-existing-jenkinshome.sh now that jenkins helm chart does this for us

Dockerfile

@@ -1,4 +1,4 @@
-FROM jenkins/jenkins:2.303.2-jdk11
+FROM jenkins/jenkins:2.303.3-jdk11
 
 USER root
 
@@ -21,17 +21,4 @@ COPY jenkins-plugins.yaml /usr/share/jenkins/ref/plugins/
 # Install plugins
 RUN jenkins-plugin-cli -f /usr/share/jenkins/ref/plugins/jenkins-plugins.yaml
 
-# check-for-existing-jenkinshome.sh is a tiny shell script that detects whether $JENKINS_HOME is an empty dir
-# if so, it creates a stub file to prevent the initialAdminPassword bootstrap behavior of the vanilla jenkins image
-# Read-only permissions are set on "${JENKINS_HOME}/plugins" because we do not want people to be able to install
-# new plugins from the UI, new plugins and plugin updates should be installed/updated via the creation of a new
-# container image
-ADD check-for-existing-jenkinshome.sh /usr/local/bin/check-for-existing-jenkinshome.sh
-RUN chmod -R 0400 "${JENKINS_HOME}/plugins"; \
-    mv /usr/local/bin/jenkins.sh /usr/local/bin/jenkins.sh.backup; \
-    cat /usr/local/bin/check-for-existing-jenkinshome.sh > /usr/local/bin/jenkins.sh; \
-    tail -n +2 /usr/local/bin/jenkins.sh.backup >> /usr/local/bin/jenkins.sh; \
-    chmod +x /usr/local/bin/jenkins.sh; \
-    rm -rf /var/jenkins_home/*
-
 USER jenkins