Add missing hyphen in arXiv badge

Author: andrewwinters5000

index.md

@@ -122,7 +122,7 @@ listed above. Author names of Trixi.jl's main developers are in *italics*.
 
 * Van Fleet, *Chan*,
   **On the choice of viscous discontinuous Galerkin discretization for entropy correction artificial viscosity methods** 2026.\\
-  [![arXiv:2602.23210](https://img.shields.io/badge/arXiv-2602.23210yellow)](https://arxiv.org/abs/2602.23210)
+  [![arXiv:2602.23210](https://img.shields.io/badge/arXiv-2602.23210-yellow)](https://arxiv.org/abs/2602.23210)
 
 * Montoya, *Rueda-Ramírez*, *Gassner*,
   **Entropy-stable discontinuous spectral-element methods for the spherical shallow water equations in covariant form**, Journal of Computational Physics (555) 114782, 2026.\\