Add a delay of 100 ms as we are overloading

the ES queue size.
Error:

12:14:44  ### Orig Err:
12:14:44  {
12:14:44    "root_cause": [
12:14:44      {
12:14:44        "type": "es_rejected_execution_exception",
12:14:44        "reason": "rejected execution of org.elasticsearch.ingest.IngestService$3@373f5932 on EsThreadPoolExecutor[name = instance-0000000015/write, queue capacity = 200, org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor@759beb77[Running, pool size = 2, active threads = 2, queued tasks = 199, completed tasks = 695890]]"
12:14:44      }

src/dev/code_coverage/shell_scripts/ingest_coverage.sh

@@ -20,6 +20,9 @@ export ES_HOST
 STATIC_SITE_URL_BASE='https://kibana-coverage.elastic.dev'
 export STATIC_SITE_URL_BASE
 
+DELAY=100
+export DELAY
+
 for x in jest functional; do
   echo "### Ingesting coverage for ${x}"