Update README.md

Removed non-working notebooks badge

Author: davidcortesortuno

README.md

@@ -10,7 +10,6 @@
 | Tests Type | Status |
 |:-:|:-:|
 | GHA Unit Tests | ![Build](https://github.com/computationalmodelling/fidimag/actions/workflows/build.yml/badge.svg?)
-| Notebooks | ![Notebooks](https://travis-matrix-badges.herokuapp.com/repos/computationalmodelling/fidimag/branches/master/2)
 
 <img src="http://computationalmodelling.github.io/fidimag/figs/skyrmion.jpg" alt="Fidimag Image" width="400" align="right">