fix: search-api/search-core/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-ORGELASTICSEARCH-7577201

search-api/search-core/pom.xml

@@ -67,7 +67,7 @@
         <dependency>
             <groupId>org.elasticsearch.client</groupId>
             <artifactId>elasticsearch-rest-high-level-client</artifactId>
-            <version>6.8.22</version>
+            <version>7.17.23</version>
         </dependency>
         <dependency>
             <groupId>junit</groupId>