fix(ci): use 512MB for elasticsearch instead of 32GB

It can be observed that when elasticsearch runs in the CI the process
uses 32GB of resident memory.

Set Xmx and Xms to no more than the threshold that the JVM uses for
compressed object pointers (compressed oops); the exact threshold
varies but is near 32 GB. You can verify that you are under the
threshold by looking for a line in the logs like the following:

Refs: https://www.elastic.co/guide/en/elasticsearch/reference/7.5/docker.html
Refs: https://www.elastic.co/guide/en/elasticsearch/reference/7.5/heap-size.html

.forgejo/workflows/testing.yml

@@ -49,6 +49,7 @@ jobs:
         image: elasticsearch:7.17.22
         env:
           discovery.type: single-node
+          ES_JAVA_OPTS: "-Xms512m -Xmx512m"
       minio:
         image: bitnami/minio:2024.3.30
         options: >-