Upgrade base elasticsearch docker image version from 7.4.2 to 8.7.1

Author: ajharry69

Dockerfile

@@ -10,6 +10,6 @@ COPY . ./
 RUN mvn package \
     && unzip target/releases/elasticsearch-analysis-dynamic-synonym-*.zip -d target/extracted
 
-FROM docker.elastic.co/elasticsearch/elasticsearch:7.4.2
+FROM docker.elastic.co/elasticsearch/elasticsearch:8.7.1
 
-COPY --from=build --chown=elasticsearch:elasticsearch /app/target/extracted /usr/share/elasticsearch/plugins/dynamic-synonym/
+COPY --from=build --chown=elasticsearch:elasticsearch /app/target/extracted /usr/share/elasticsearch/plugins/dynamic-synonym/