[Java] Disable the multi-worker feature by default (#10593)

java/runtime/src/main/resources/ray.default.conf

@@ -27,7 +27,7 @@ ray {
     // the path for job 123 will be '/tmp/job_resources/123'.
     resource-path: ""
     /// The number of java worker per worker process.
-    num-java-workers-per-process: 10
+    num-java-workers-per-process: 1
     /// The jvm options for java workers of the job.
     jvm-options: []
     // Environment variables to be set on worker processes.
@@ -98,7 +98,6 @@ ray {
   raylet {
     // See src/ray/ray_config_def.h for options.
     config {
-      num_workers_per_process_java: 10
       // TODO(zhuohan): enable this for java
       put_small_object_in_memory_store: false
     }