CI: Update Qt path on Windows

AppVeyor recently updated their Qt version to 5.11.2 which breaks
builds, because of the outdated path. Using this path should always
ensure that the newest subversion of Qt 5.11 gets used.

CI/install-script-win.cmd

@@ -9,8 +9,8 @@ if exist cef_binary_%CEF_VERSION%_windows64.zip (curl -kLO https://obsproject.co
 set DepsPath32=%CD%\dependencies2017\win32
 set DepsPath64=%CD%\dependencies2017\win64
 set VLCPath=%CD%\vlc
-set QTDIR32=C:\Qt\5.11.1\msvc2015
-set QTDIR64=C:\Qt\5.11.1\msvc2017_64
+set QTDIR32=C:\Qt\5.11\msvc2015
+set QTDIR64=C:\Qt\5.11\msvc2017_64
 set CEF_32=%CD%\CEF_32\cef_binary_%CEF_VERSION%_windows32
 set CEF_64=%CD%\CEF_64\cef_binary_%CEF_VERSION%_windows64
 set build_config=RelWithDebInfo