checkstyle: Fix disagreement between checkstyle and google-java-format

If there is an import starting with 'vendor', google-java-format expects
it to appear before the 'java' group. Update config to match.

Bug: b/328800452
Test: checkstyle no longer complains about google-java-format'd code
Change-Id: I48725b37b99bff3eb209b60520cd99b0b0ac2fed
diff --git a/default-treewalker-checks.xml b/default-treewalker-checks.xml
index 62f40c0..4c75318 100644
--- a/default-treewalker-checks.xml
+++ b/default-treewalker-checks.xml
@@ -154,7 +154,7 @@
 <module name="ImportOrder">
   <property name="severity" value="error"/>
   <message key="import.ordering" value="Wrong order for {0} import. Use Ctrl+Shift+O (Eclipse) or Ctrl+Alt+O (Intellij) to sort imports. https://source.android.com/setup/code-style#order-import-statements"/>
-  <property name="groups" value="android, androidx, com.android, dalvik, com, dagger, gov, io, junit, junitparams, libcore, net, kotlin, org, perfetto, java, javax"/>
+  <property name="groups" value="android, androidx, com.android, dalvik, com, dagger, gov, io, junit, junitparams, libcore, net, kotlin, org, perfetto, vendor, java, javax"/>
   <property name="ordered" value="true"/>
   <property name="option" value="top"/>
   <property name="separated" value="true"/>