fix booklet build (#5682)

Author: krasinski

booklet/src/sections/intro.tex

@@ -152,7 +152,7 @@
     \begin{itemize}
         \item Linux/OS X/Windows
         \item Java 8 or higher
-        \item Python SUBST_MIN_SUPPORTED_PYTHON+ For Python version of Sparkling Water (PySparkling)
+        \item Python 3.6+ For Python version of Sparkling Water (PySparkling)
         \item R 3.4+ for R version of Sparkling Water (RSparkling)
         \item Installed Spark and have SPARK\_HOME environmental variable pointing to its home.
     \end{itemize}