update release ch 26

Author: sbonaretti

assets/book/learn_python_with_jupyter.pdf

@@ -240,7 +240,7 @@ <h2>About the Book</h2>
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-            <center>Next upload: <b>Chapter 26</b> on <b>April 21</b> </center>
+            <center>Next upload: <b>Chapter 26</b> on <b>April 24</b> </center>
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