Docs: Fix PASC Paper Formatting

Docs/source/highlights.rst

@@ -27,7 +27,7 @@ Scientific works in laser-plasma and beam-plasma acceleration.
 #. Sandberg R T, Lehe R, Mitchell C E, Garten M, Myers A, Qiang J, Vay J-L and Huebl A.
   **Synthesizing Particle-in-Cell Simulations Through Learning and GPU Computing for Hybrid Particle Accelerator Beamlines**.
   Proc. of Platform for Advanced Scientific Computing (PASC'24), *submitted*, 2024.
-  `preprint <http://arxiv.org/abs/2402.17248>__`
+  `preprint <http://arxiv.org/abs/2402.17248>`__
 
 #. Sandberg R T, Lehe R, Mitchell C E, Garten M, Qiang J, Vay J-L and Huebl A.
    **Hybrid Beamline Element ML-Training for Surrogates in the ImpactX Beam-Dynamics Code**.
@@ -104,7 +104,7 @@ Scientific works in particle and beam modeling.
 #. Sandberg R T, Lehe R, Mitchell C E, Garten M, Myers A, Qiang J, Vay J-L and Huebl A.
   **Synthesizing Particle-in-Cell Simulations Through Learning and GPU Computing for Hybrid Particle Accelerator Beamlines**.
   Proc. of Platform for Advanced Scientific Computing (PASC'24), *submitted*, 2024.
-  `preprint <http://arxiv.org/abs/2402.17248>__`
+  `preprint <http://arxiv.org/abs/2402.17248>`__
 
 #. Sandberg R T, Lehe R, Mitchell C E, Garten M, Qiang J, Vay J-L, Huebl A.
    **Hybrid Beamline Element ML-Training for Surrogates in the ImpactX Beam-Dynamics Code**.