screenshots: Run on Windows 10, try to fix resolution

T141369 still applies apparently, so switch back to Windows 10.

Switching to Linux did fix the screen resolution, so try setting
one manually instead.

Change-Id: I3d42fd972f1dbad4302cac1e7e5f052b6cfdb600

build/screenshots.js

@@ -19,6 +19,7 @@ function createScreenshotEnvironment( test ) {
 			driver = new webdriver.Builder().withCapabilities( {
 				browserName: process.env.BROWSER,
 				platform: process.env.PLATFORM,
+				screenResolution: '1280x1024',
 				username: username,
 				accessKey: accessKey
 			} ).usingServer( 'http://' + username + ':' + accessKey +

build/screenshots.yml

@@ -2,4 +2,4 @@ BROWSER:
   - chrome
 
 PLATFORM:
-  - Linux
+  - Windows 10