Fix gitattributes to suppress diffs too

Author: myitcv

.gitattributes

@@ -1,3 +1,6 @@
-_vendor/**/* linguist-vendored
+/_vendor/* linguist-vendored
+/_vendor/* linguist-generated=true
 examples/sites/common/* linguist-vendored
+examples/sites/common/* linguist-generated=true
 *.inc.js linguist-vendored
+*.inc.js linguist-generated=true