CE-4770: Undo elaticsearch upgrade

It have to be done later in a separate pull request.

Author: Domonkos Gulyas

README.md

@@ -46,7 +46,7 @@ For using docker containers there is a barebones [docker compose file](./compose
 * Prerequisites
 
     * JDK 21
-    * Elastic version 8.18.x
+    * Elastic version 8.11.x
     * **For authN/authZ using LDAP:** LDAP server, e.g. OpenLDAP
 
 #### Setup Elasticsearch

compose.yml

@@ -15,7 +15,7 @@ services:
         condition: service_healthy
 
   elasticsearch:
-    image: docker.elastic.co/elasticsearch/elasticsearch:8.18.0
+    image: docker.elastic.co/elasticsearch/elasticsearch:8.11.2
     hostname: elasticsearch
     networks:
       - channelfinder-net

pom.xml

@@ -37,7 +37,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <spring.boot-version>3.4.4</spring.boot-version>
         <jackson.version>2.18.3</jackson.version>
-        <elasticsearch.version>8.18.0</elasticsearch.version>
+        <elasticsearch.version>8.11.2</elasticsearch.version>
         <junit-jupiter.version>5.10.0</junit-jupiter.version>
         <skipITs>true</skipITs>
         <skipITCoverage>true</skipITCoverage>