quickfix for WebViewActivityTest

URL for Webview was recently updated and must be
adapted for testcase

failing testcase: https://jenkins.catrob.at/job/Catroid-Multi-Job/84/testReport/junit/org.catrobat.catroid.uitest.ui.activity/WebViewActivityTest/testWebView/
single ui test on emulator: https://jenkins.catrob.at/job/Catroid-single-UI-emulator/138/