Reverting undesired change in Rakefile

Author: diemol

Rakefile

@@ -892,7 +892,7 @@ namespace :dotnet do
       sh 'docfx dotnet/docs/docfx.json'
     rescue StandardError
       case $CHILD_STATUS.exitstatus
-      when 136
+      when 133
         raise 'Ensure the dotnet/tools directory is added to your PATH environment variable (e.g., `~/.dotnet/tools`)'
       when 255
         puts '.NET documentation build failed, likely because of DevTools namespacing. This is ok; continuing'