stop using Google mirror for tests

Author: chingor13

settings.xml

@@ -18,15 +18,7 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
                           https://maven.apache.org/xsd/settings-1.0.0.xsd">
-  <mirrors>
-    <mirror>
-      <!-- Google's Maven Central mirror for Americas
-       https://maven-central.storage.googleapis.com/index.html
-      -->
-      <id>google-maven-central</id>
-      <name>GCS Maven Central mirror</name>
-      <url>https://maven-central.storage-download.googleapis.com/maven2/</url>
-      <mirrorOf>central</mirrorOf>
-    </mirror>
-  </mirrors>
+  <!-- This file contains settings used by .kokoro/build.sh. These are global
+   configs used by almost every build script.
+  -->
 </settings>