Enable the IgnoreClassLevelDetector lint check for test files

This should have been included in the original Cl (aosp/2105185)

Test: Creating the error in a test file and checking that the lint catches it
Bug: 233355288
Change-Id: I911073660c5f760f4b1fbc4fa710a163b1d6ddd8
diff --git a/buildSrc/lint.xml b/buildSrc/lint.xml
index 693786b..72bcf5b 100644
--- a/buildSrc/lint.xml
+++ b/buildSrc/lint.xml
@@ -38,4 +38,5 @@
     <issue id="NewApi" severity="fatal" />
     <issue id="WrongThread" severity="fatal" />
     <issue id="MissingTestSizeAnnotation" severity="fatal" />
+    <issue id="IgnoreClassLevelDetector" severity="fatal" />
 </lint>