docs: update ref typo

Author: jelledouwe

docs/index.rst

@@ -147,7 +147,7 @@ If you are using EAGERx for your scientific publications, please cite:
 
    @article{vanderheijden2024eagerx,
      author={van der Heijden, Bas and Luijkx, Jelle and Ferranti, Laura and Kober, Jens and Babuska, Robert},
-     journal={IEEE Robotics & Automation Magazine}, 
+     journal={IEEE Robotics \& Automation Magazine}, 
      title={Engine Agnostic Graph Environments for Robotics (EAGERx): A Graph-Based Framework for Sim2real Robot Learning}, 
      year={2024},
      volume={},