update xcode version in travis

tristanhimmelman · tristanhimmelman · commit dadb9fde3c6b · 2020-03-15T20:58:09.000-04:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,5 @@
 language: objective-c
-osx_image: xcode9.4
+osx_image: xcode11.3
 
 env:
   global:
