build: reduce download junk in log files (#380)

This PR was generated using Autosynth. 🌈

Synth log will be available here:
https://source.cloud.google.com/results/invocations/c662ff13-a77b-48b5-be4e-62774692925a/targets

- [ ] To automatically regenerate this PR, check this box.

Source-Link: googleapis/synthtool@6946fd7

java-core/.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 \

java-core/.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

java-core/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-core.git",
-        "sha": "b0c0a20301fd324cc2cbc7f2da65521232cb367a"
+        "sha": "d95ccb1fd7c8513ffd57ecd9723b68dd517b1a4a"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "1aeca92e4a38f47134cb955f52ea76f84f09ff88"
+        "sha": "6946fd71ae9215b0e7ae188f5057df765ee6d7d2"
       }
     }
   ],