Disable transfer logging during version lookup.

Compare
b7e5b88.

I'm hoping that this is the only remaining source of [the remaining such
logging](https://github.com/google/guava/actions/runs/20937533296/job/60165108176#step:4:10):

```
Run ./util/update_snapshot_docs.sh
Publishing Javadoc and JDiff...
Checking out 'master'... Done.
Pulling to get latest changes... Done.
WARNING: A restricted method in java.lang.System has been called
WARNING: java.lang.System::load has been called by org.fusesource.jansi.internal.JansiLoader in an unnamed module (file:/home/runner/.m2/wrapper/dists/apache-maven-3.9.12-bin/78a7b4ce/apache-maven-3.9.12/lib/jansi-2.4.2.jar)
WARNING: Use --enable-native-access=ALL-UNNAMED to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled

[INFO] Scanning for projects...
[INFO] Inspecting build with total of 2 modules
[INFO] Installing Central Publishing features
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO]
[INFO] Guava Maven Parent                                                 [pom]
[INFO] Guava: Google Core Libraries for Java                           [bundle]
[INFO]
[INFO] -------------------< com.google.guava:guava-parent >--------------------
[INFO] Building Guava Maven Parent 999.0.0-HEAD-jre-SNAPSHOT              [1/2]
[INFO]   from pom.xml
[INFO] --------------------------------[ pom ]---------------------------------
Downloading from central: https://repo.maven.apache.org/maven2/com/diamondq/maven/javahome-resolver-maven-plugin/1.0.2/javahome-resolver-maven-plugin-1.0.2.pom
Progress (1): 1.0 kB
Progress (1): 2.3 kB
Progress (1): 8.2 kB
Progress (1): 16 kB
Progress (1): 20 kB
Progress (1): 23 kB
```

(And there's [more further
down](https://github.com/google/guava/actions/runs/20937533296/job/60165108176#step:4:140).)

Author: cpovirk

_util/util.sh

@@ -29,6 +29,7 @@ function guava_version {
     mvnw=../mvnw # We're in the android subdirectory of the main directory.
   fi
   "${mvnw}" org.apache.maven.plugins:maven-help-plugin:2.1.1:evaluate \
+      -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=warn \
       -Dexpression=project.version \
       -pl guava 2> /dev/null \
       | grep -Ev '(^\[|Download.+:)'