Use static black logo for Gitea (no theme switch)

README.md

@@ -1,9 +1,5 @@
 <div align="center">
-  <picture>
-    <source media="(prefers-color-scheme: dark)" srcset="./assets/hellion-online-media-dark.png">
-    <source media="(prefers-color-scheme: light)" srcset="./assets/hellion-online-media-light.png">
   <img src="./assets/hellion-online-media-light.png" alt="Hellion Online Media" width="640">
-  </picture>
 </div>
 
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