Resolve "Blog Post: Advertise Helmholtz GPU Hackathon"

Closes #425 (closed)

_posts/2023/2023-01-20-helmholtz-gpu-hackathon.md

@@ -37,7 +37,8 @@ The Helmholtz GPU Hackathon will be hosted **primarily onsite** at the Jülich S
 
 You can find out more and register at the [website of the event](https://www.helmholtz-hida.de/en/events/helmholtz-gpu-hackathon-2023/).
 
-==Deadline for the team application is March 14, 2023!==
+{:.summary}
+**Deadline for the team application is March 14, 2023!**
 
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