There is a solution to this on Yosemite. It is to create a dummy Xcode application in the applications folder, then Spotlight will think you are a dev and allow you to turn it developer search results off.
To create the dummy Xcode app you have to go in to terminal and paste these separately otherwise it'll not work...
Code:
cd /Applications
touch Xcode.app
Then go into system preferences and uncheck "Developer" form Spotlight searches. You may have to reopen system preferences to see the option appear...
Then open another terminal window and paste this to hide the dummy app, don't worry as spotlight will still think Xcode is installed
Code:
chflags hidden /Applications/Xcode.app
And there you are developer search results are hidden on Yosemite