build(java): enable blunderbuss for samples (#1191)

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Synth log will be available here:
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Source-Link: googleapis/synthtool@943bb78

Author: yoshi-automation

.github/blunderbuss.yml

@@ -0,0 +1,7 @@
+# Configuration for the Blunderbuss GitHub app. For more info see
+# https://github.com/googleapis/repo-automation-bots/tree/master/packages/blunderbuss
+assign_prs_by:
+- labels:
+  - samples
+  to:
+  - googleapis/java-samples-reviewers

synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/google-http-java-client.git",
-        "sha": "74b15e238a286ca4565e7dd65d94025b77543cf9"
+        "sha": "484303d9b20edc974b7590d6fab7ef32ef14c1bc"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "68742c6016bf0d16948a572633d17955a8737414"
+        "sha": "943bb78606d035001123030067dffcc34f4645f2"
       }
     }
   ],
@@ -21,6 +21,7 @@
     ".github/ISSUE_TEMPLATE/feature_request.md",
     ".github/ISSUE_TEMPLATE/support_request.md",
     ".github/PULL_REQUEST_TEMPLATE.md",
+    ".github/blunderbuss.yml",
     ".github/generated-files-bot.yml",
     ".github/readme/synth.py",
     ".github/release-please.yml",