[GR-16675] Fix CHANGELOG.

Author: ansalond

CHANGELOG.md

@@ -3,14 +3,11 @@
 This changelog summarizes major changes between GraalVM versions of the Python
 language runtime. The main focus is on user-observable behavior of the engine.
 
-## Version 20.0.0 beta 2
+## Version 19.1.0
 
 * Add `java.add_to_classpath` API to dynamically extend the host class path
 * Allow write access to main module bindings for embedder
 * Swap arguments for `polyglot.export_value` to use the more natural (name, value) order and deprecate the previous argument order.
-
-## Version 20.0.0 beta 1
-
 * Update Python standard library files to Python 3.7.3
 * Improve performance of exceptions that do not escape
 * Fix str(None) to print "None" instead of an empty string