Yes!
Log in to Travis CI (travis-ci.org) under your account.
Then check on the left sidebar. You should see a My repositories label followed by a plus sign (i.e. +).
Click on that plus sign (i.e. +).
It will lead you to a page listing all your Github repositories with an on/off toggle beside each one.
Just put the toggle to “off” for the repositories you don’t want in Travis CI.
Hope this helps!