It's great to include an opportunity for your mailing recipients to share your content on their social platforms, but perhaps you're sending an internal mailing that you'd rather not be shared. In that case, you can turn off the Share this email block from appearing, when you're using one of the templates from the gallery.
While editing your mailing, click the Share this email block in the footer. This opens the Email, Twitter, Facebook and LinkedIn options, and you can uncheck the ones that shouldn't display.
Uncheck all four to remove them all, and you'll see that the Share this email block changes to show that no items are selected.
Then your footer will arrive to the inbox like this: