docs: update to use correct PIA SVG logo

- Use official SVG logo from https://programintegrity.org/wp-content/uploads/2024/07/PIA-Logo.svg
- SVG format provides better quality and scalability
- Corrects logo URL to use the most current version
- Maintains same visual design and branding

Author: dividor

README.md

@@ -6,7 +6,7 @@
 
 <div align="center">
   <a href="https://programintegrity.org/">
-    <img src="https://programintegrity.org/wp-content/uploads/2024/01/pia-logo-horizontal.png" alt="Program Integrity Alliance" width="400"/>
+    <img src="https://programintegrity.org/wp-content/uploads/2024/07/PIA-Logo.svg" alt="Program Integrity Alliance" width="400"/>
   </a>
 </div>