remove xvfb from sheriff-o-matic makefile

BUG=404414
R=ojan@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/483773004

git-svn-id: svn://svn.chromium.org/blink/trunk@180484 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Tools/GardeningServer/makefile

@@ -19,9 +19,9 @@ update: check
 	npm update
 
 test: check
-	xvfb-run ./node_modules/karma/bin/karma start
+	./node_modules/karma/bin/karma start
 
 single-test: check
-	xvfb-run ./node_modules/karma/bin/karma start --single-run
+	./node_modules/karma/bin/karma start --single-run
 
 .PHONY: check update test single-test