Fix compat test

Author: thesamet

e2e.sh

@@ -2,11 +2,11 @@
 set -e
 SCALA_VERSION=${SCALA_VERSION:-2_12}
 if [[ "$SCALA_VERSION" != "2_12" ]]; then
-    COMPAT_TARGET=e2eScala3SourcesJVM${SCALA_VERSION};
+    COMPAT_TARGET=e2eScala3SourcesJVM${SCALA_VERSION}/test;
 fi
 
 sbt clean \
     e2eJVM$SCALA_VERSION/test \
     e2eGrpcJVM$SCALA_VERSION/test \
     e2eJS${SCALA_VERSION}/test \
-    $COMPAT_TARGET/test
+    $COMPAT_TARGET