Change logo width from 80% to 50%

Updated logo image width in README.

Author: sydney-runkle

README.md

@@ -1,7 +1,7 @@
 <picture class="github-only">
   <source media="(prefers-color-scheme: light)" srcset=".github/images/logo-light.svg">
   <source media="(prefers-color-scheme: dark)" srcset=".github/images/logo-dark.svg">
-  <img alt="LangGraph Logo" src=".github/images/logo-dark.svg" width="80%">
+  <img alt="LangGraph Logo" src=".github/images/logo-dark.svg" width="50%">
 </picture>
 
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