chore(java): use production staging bucket (#317)

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Source-Link: googleapis/synthtool@c7824ea

.kokoro/release/publish_javadoc.cfg

@@ -9,7 +9,7 @@ env_vars: {
 
 env_vars: {
   key: "STAGING_BUCKET_V2"
-  value: "docs-staging-v2-staging"
+  value: "docs-staging-v2"
   # Production will be at: docs-staging-v2
 }
 

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-datalabeling.git",
-        "sha": "aaa615f834d778fd7101801b360c794ae841e07f"
+        "sha": "66041b9a6eed1d97c3413b78246390054d71bd74"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "b19b401571e77192f8dd38eab5fb2300a0de9324"
+        "sha": "c7824ea48ff6d4d42dfae0849aec8a85acd90bd9"
       }
     }
   ],