revisit the README file

Author: tschm

README.md

@@ -22,9 +22,6 @@
     <a href="https://pepy.tech/project/pyportfolioopt">
         <img src="https://pepy.tech/badge/pyportfolioopt"
             alt="downloads"></a> &nbsp;
-    <a href="https://mybinder.org/v2/gh/pyportfolio/pyportfolioopt/main/?filepath=cookbook">
-      <img src="https://mybinder.org/badge_logo.svg"
-            alt="binder"></a> &nbsp;
 </p>
 
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