Fix JSON path file ending

Changelog: fixed

src/gitlab-tofu.sh

@@ -184,7 +184,7 @@ should_init_without_reconfigure=${GITLAB_TOFU_INIT_NO_RECONFIGURE:-false}
 # Plan variables
 apply_without_plan=${GITLAB_TOFU_APPLY_NO_PLAN:-false}
 plan_cache_path="${GITLAB_TOFU_PLAN_CACHE:-${default_tf_plan_cache:-${base_plan_name}.cache}}"
-plan_json_path="${GITLAB_TOFU_PLAN_JSON:-${default_tf_plan_json:-${base_plan_name}.cache}}"
+plan_json_path="${GITLAB_TOFU_PLAN_JSON:-${default_tf_plan_json:-${base_plan_name}.json}}"
 plan_with_detailed_exitcode=${GITLAB_TOFU_USE_DETAILED_EXITCODE:-false}
 plan_with_json_file=${GITLAB_TOFU_PLAN_WITH_JSON:-false}
 plan_jq_filter='