update test cookbook since 9.3 can't install on Sierra

test/cookbooks/macos_test/recipes/xcode.rb

@@ -1,12 +1,16 @@
-if node['platform_version'].match? Regexp.union ['10.12', '10.13']
+if node['platform_version'].match? Regexp.union '10.13'
   execute 'Disable Gatekeeper' do
     command ['spctl', '--master-disable']
   end
 
   include_recipe 'macos::xcode'
 
-elsif node['platform_version'].match? Regexp.union '10.11'
+elsif node['platform_version'].match? Regexp.union '10.12'
+  xcode '9.2' do
+    ios_simulators %w(11 10)
+  end
 
+elsif node['platform_version'].match? Regexp.union '10.11'
   xcode '8.2.1' do
     ios_simulators %w(10 9)
   end

test/cookbooks/macos_test/recipes/xcode_beta.rb

@@ -1,7 +1,5 @@
-if node['platform_version'].match? Regexp.union ['10.12', '10.13']
-  execute 'Disable Gatekeeper' do
-    command ['spctl', '--master-disable']
-  end
-
-  xcode '9.4'
+execute 'Disable Gatekeeper' do
+  command ['spctl', '--master-disable']
 end
+
+xcode '9.4'