build: reduce download junk in log files (#514)

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Synth log will be available here:
https://source.cloud.google.com/results/invocations/d609e2d2-1c7e-41bf-b80a-341f534a34a8/targets

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Source-Link: googleapis/synthtool@6946fd7

.kokoro/build.sh

@@ -29,7 +29,7 @@ echo ${JOB_TYPE}
 
 # attempt to install 3 times with exponential backoff (starting with 10 seconds)
 retry_with_backoff 3 10 \
-  mvn install -B -V \
+  mvn install -B -V -ntp \
     -DskipTests=true \
     -Dclirr.skip=true \
     -Denforcer.skip=true \

.kokoro/dependencies.sh

@@ -31,7 +31,7 @@ export MAVEN_OPTS="-Xmx1024m -XX:MaxPermSize=128m"
 
 # this should run maven enforcer
 retry_with_backoff 3 10 \
-  mvn install -B -V \
+  mvn install -B -V -ntp \
     -DskipTests=true \
     -Dclirr.skip=true
 
@@ -86,4 +86,4 @@ then
 else
   msg "Errors found. See log statements above."
   exit 1
-fi
+fi

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-pubsub.git",
-        "sha": "98d53168d72f8c94fdc1315dad57cbbe1f1bcfac"
+        "sha": "3c478ec68afb8426ba5e670c563a7a925e431d85"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "1aeca92e4a38f47134cb955f52ea76f84f09ff88"
+        "sha": "6946fd71ae9215b0e7ae188f5057df765ee6d7d2"
       }
     }
   ],