chore: turn on renovate-bot master issue for java repos (#119)

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Synth log will be available here:
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Source-Link: googleapis/synthtool@cac9eef

renovate.json

@@ -76,5 +76,6 @@
       "groupName": "jackson dependencies"
     }
   ],
-  "semanticCommits": true
+  "semanticCommits": true,
+  "masterIssue": true
 }

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-monitoring-dashboards.git",
-        "sha": "7bb2da1bd15bfedb2e5eb7ebc0a0700bf2a39cfb"
+        "sha": "93d6f6b4e249b82e085940fc01bbf3c41ae2e6f0"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "8b65daa222d193b689279162781baf0aa1f0ffd2"
+        "sha": "cac9eef310652bf138dd76b716e4986e757d62ac"
       }
     }
   ],