build(java): enable snippet-bot (googleapis#257)

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Synth log will be available here:
https://source.cloud.google.com/results/invocations/35a5efff-460c-411a-ad03-b70aaaa0fe6f/targets

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Source-Link: googleapis/synthtool@5a506ec

synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-storage-nio.git",
-        "sha": "c59cc46fe270080eca7ac56d25c5bb90e7b0841c"
+        "sha": "73d7dd2ec6ca371480955c844ffb5e6aed4f608f"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "7c5370937dd9ba9dcf9cd7d2af880a58b389b4f1"
+        "sha": "5a506ec8765cc04f7e29f888b8e9b257d9a7ae11"
       }
     }
   ],
@@ -23,6 +23,7 @@
     ".github/PULL_REQUEST_TEMPLATE.md",
     ".github/readme/synth.py",
     ".github/release-please.yml",
+    ".github/snippet-bot.yml",
     ".github/trusted-contribution.yml",
     ".github/workflows/approve-readme.yaml",
     ".github/workflows/auto-release.yaml",