1) Go to Template > Edit HTML
2) Click anywhere in the HTML script and press ctrl+F to open up finder
3) Copy and paste the link below in the search box and delete it.
If you are having trouble finding it in your search bar, sometimes it helps to just search for part of the code. Just make sure you delete the whole section.
<b:include data='feedLinks' name='feedLinksBody'/>
That's all there is to it! The Subscribe to Posts (Atom) link should be gone.
Need to remove Subscribe to Post Comments (Atom) link on your individual posts? Follow this tutorial to remove the link!