Update version check images to use SVG

CHANGELOG

@@ -18,6 +18,7 @@ v 8.4.0 (unreleased)
   - Fix version check image in Safari
   - Show 'All' tab by default in the builds page
   - Fix API project lookups when querying with a namespace with dots (Stan Hu)
+  - Update version check images to use SVG
 
 v 8.3.3 (unreleased)
   - Fix project transfer e-mail sending incorrect paths in e-mail notification (Stan Hu)

lib/version_check.rb

@@ -13,6 +13,6 @@ class VersionCheck
   end
 
   def host
-    'https://version.gitlab.com/check.png'
+    'https://version.gitlab.com/check.svg'
   end
 end