idempotent pipeline timeline sql change (#6554)

Author: kartik-579

scripts/sql/32903500_alter_pipeline_timeline.up.sql

@@ -1,3 +1,3 @@
-CREATE INDEX "idx_pipeline_status_timeline_cd_workflow_runner_id" ON pipeline_status_timeline USING BTREE ("cd_workflow_runner_id");
+CREATE INDEX IF NOT EXISTS "idx_pipeline_status_timeline_cd_workflow_runner_id" ON pipeline_status_timeline USING BTREE ("cd_workflow_runner_id");
 
-CREATE INDEX "idx_pipeline_status_timeline_installed_app_version_history_id" ON pipeline_status_timeline USING BTREE ("installed_app_version_history_id");
+CREATE INDEX IF NOT EXISTS "idx_pipeline_status_timeline_installed_app_version_history_id" ON pipeline_status_timeline USING BTREE ("installed_app_version_history_id");