Fix Python support in installation instructions

Author: dflook

docs/source/installation.rst

@@ -13,4 +13,4 @@ and outputs source code compatible with the version of the interpreter it is run
 This means that if you minify code written for Python 3.6 using python-minifier running with Python 3.12,
 the minified code may only run with Python 3.12.
 
-python-minifier runs with and can minify code written for Python 2.7 and Python 3.3 to 3.12.
+python-minifier runs with and can minify code written for Python 2.7 and Python 3.3 to 3.13.