runner: Remove the ability to use the deprecated --once flag

Ref #1196

README.md

@@ -1298,13 +1298,6 @@ spec:
         # Disables automatic runner updates
         - name: DISABLE_RUNNER_UPDATE
           value: "true"
-        # Configure runner with --ephemeral instead of --once flag
-        # WARNING | THIS ENV VAR IS DEPRECATED AND WILL BE REMOVED
-        # IN A FUTURE VERSION OF ARC. IN 0.22.0 ARC SETS --ephemeral VIA 
-        # THE CONTROLLER SETTING THIS ENV VAR ON POD CREATION.
-        # THIS ENV VAR WILL BE REMOVED, SEE ISSUE #1196 FOR DETAILS
-        - name: RUNNER_FEATURE_FLAG_EPHEMERAL
-          value: "true"
 ```
 
 ### Using IRSA (IAM Roles for Service Accounts) in EKS

runner/entrypoint.sh

@@ -76,7 +76,7 @@ cd ${RUNNER_HOME}
 # past that point, it's all relative pathes from /runner
 
 config_args=()
-if [ "${RUNNER_FEATURE_FLAG_EPHEMERAL:-}" == "true" -a "${RUNNER_EPHEMERAL}" == "true" ]; then
+if [ "${RUNNER_EPHEMERAL}" == "true" ]; then
   config_args+=(--ephemeral)
   log.debug 'Passing --ephemeral to config.sh to enable the ephemeral runner.'
 fi
@@ -140,15 +140,6 @@ if [ -z "${UNITTEST:-}" ]; then
   mv ./externalstmp/* ./externals/
 fi
 
-args=()
-if [ "${RUNNER_FEATURE_FLAG_EPHEMERAL:-}" != "true" -a "${RUNNER_EPHEMERAL}" == "true" ]; then
-  args+=(--once)
-  log.warning 'Passing --once is deprecated and will be removed as an option' \
-    'from the image and actions-runner-controller at the release of 0.24.0.' \
-    'Upgrade to GHES => 3.3 to continue using actions-runner-controller. If' \
-    'you are using github.com ignore this warning.'
-fi
-
 # Unset entrypoint environment variables so they don't leak into the runner environment
 unset RUNNER_NAME RUNNER_REPO RUNNER_TOKEN STARTUP_DELAY_IN_SECONDS DISABLE_WAIT_FOR_DOCKER