Add one more directory from Maven build to .gitignore

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1888431 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/.gitignore b/.gitignore
index 97b2d36..0ba0c1b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -28,6 +28,7 @@
 sonar/ooxml-full/src/
 sonar/examples/src/
 sonar/excelant/src/
+sonar/integration-test/src/
 sonar/target
 sonar/*/target