Fix warning "calling yaml.load() without Loader=... is deprecated"

in gen-yml-from-env.py

docker/pulsar/scripts/gen-yml-from-env.py

@@ -61,7 +61,7 @@
 conf_files = sys.argv[1:]
 
 for conf_filename in conf_files:
-    conf = yaml.load(open(conf_filename))
+    conf = yaml.load(open(conf_filename), Loader=yaml.FullLoader)
 
     # update the config
     modified = False