Remove deprecated allowEmptyFolder CLI option

The allowEmptyFolder option is no longer functional because:
1. The code that used it was already commented out
2. Empty folder cleanup is now handled asynchronously by EmptyFolderCleaner

The CLI flags are kept for backward compatibility but marked as deprecated
and ignored. This removes:
- S3ApiServerOption.AllowEmptyFolder field
- The actual usage in s3api_object_handlers_list.go
- Helm chart values and template references
- References in test Makefiles and docker-compose files

Makefile

@@ -18,12 +18,12 @@ full_install: admin-generate
 	cd weed; go install -tags "elastic gocdk sqlite ydb tarantool tikv rclone"
 
 server: install
-	weed -v 0 server -s3 -filer -filer.maxMB=64 -volume.max=0 -master.volumeSizeLimitMB=100 -volume.preStopSeconds=1 -s3.port=8000 -s3.allowEmptyFolder=false -s3.allowDeleteBucketNotEmpty=true -s3.config=./docker/compose/s3.json -metricsPort=9324
+	weed -v 0 server -s3 -filer -filer.maxMB=64 -volume.max=0 -master.volumeSizeLimitMB=100 -volume.preStopSeconds=1 -s3.port=8000 -s3.allowDeleteBucketNotEmpty=true -s3.config=./docker/compose/s3.json -metricsPort=9324
 
 benchmark: install warp_install
 	pkill weed || true
 	pkill warp || true
-	weed server -debug=$(debug) -s3 -filer -volume.max=0 -master.volumeSizeLimitMB=100 -volume.preStopSeconds=1 -s3.port=8000 -s3.allowEmptyFolder=false -s3.allowDeleteBucketNotEmpty=false -s3.config=./docker/compose/s3.json &
+	weed server -debug=$(debug) -s3 -filer -volume.max=0 -master.volumeSizeLimitMB=100 -volume.preStopSeconds=1 -s3.port=8000 -s3.allowDeleteBucketNotEmpty=false -s3.config=./docker/compose/s3.json &
 	warp client &
 	while ! nc -z localhost 8000 ; do sleep 1 ; done
 	warp mixed --host=127.0.0.1:8000 --access-key=some_access_key1 --secret-key=some_secret_key1 --autoterm