[CI] Remove lint step from unity/pr-head step (#17155)

* [CI] Remove lint step from `unity/pr-head` step

This step should only be performed as part of the `lint/pr-head` CI
step.  It was included as part of the unity-specific CI steps prior to
merging of unity into main.  It is no longer necessary as part of
`unity/pr-head`.

* Revert the task_extra_lint.sh removal

ci/jenkins/unity_jenkinsfile.groovy

@@ -210,14 +210,6 @@ def lint(node_type) {
           )
           skip_ci = should_skip_ci(env.CHANGE_ID)
           skip_slow_tests = should_skip_slow_tests(env.CHANGE_ID)
-          sh(
-            script: "${docker_run} ${ci_lint}  ./tests/scripts/task_lint.sh",
-            label: 'Run lint',
-          )
-          sh(
-            script: "${docker_run} ${ci_lint}  ./tests/scripts/unity/task_extra_lint.sh",
-            label: 'Run extra lint',
-          )
         }
       }
     }