Fix trivial logo image URL problem (#47)

Image URLs need to be absolute, not relative, in order for images to
show up on PyPI.

Author: mhucka

README.md

@@ -114,6 +114,6 @@ Copyright 2025 Google LLC.
 <div align="center">
   <a href="https://quantumai.google">
     <img width="15%" alt="Google Quantum AI"
-         src="./assets/quantum-ai-vertical.svg">
+         src="https://raw.githubusercontent.com/quantumlib/chromobius/refs/heads/main/assets/quantum-ai-vertical.svg">
   </a>
 </div>