fix typo in variables overrides

projects/local_ci/toolbox/local_ci_run/templates/pod.yaml.j2

@@ -76,7 +76,7 @@ spec:
       trap 'echo $? > "$ARTIFACT_DIR/.local_ci_done"' ERR
 
       cat > "$ARTIFACT_DIR/variable_overrides.yaml" <<EOF
-      PR_POSITIONAL_ARG_0="{{ local_ci_run_test_name }}"
+      PR_POSITIONAL_ARG_0: "{{ local_ci_run_test_name }}"
 {% for element in local_ci_run_test_args or [] %}
       PR_POSITIONAL_ARG_{{loop.index}}: "{{ element }}"
 {% endfor %}