fix: update cognee logo on readme (#559)

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## Description
<!-- Provide a clear description of the changes in this PR -->

## DCO Affirmation
I affirm that all code in every commit of this pull request conforms to
the terms of the Topoteretes Developer Certificate of Origin


<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

- **Documentation**
- Updated the project's logo image in the documentation to a transparent
version for a cleaner, more modern visual presentation.
  - Increased the logo height for improved visibility.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

README.md

@@ -2,11 +2,10 @@
 <br />
 <div align="center">
   <a href="https://github.com/topoteretes/cognee">
-    <img src="./assets/cognee_logo.png" alt="Logo" height="95">
+    <img src="./assets/cognee_logo_transparent.png" alt="Logo" height="150">
   </a>
 
   <br />
-  <br />