Update README.rst - Add missing comma in the list of acknowlegements (pybind#4750)

Author: bzaar

README.rst

@@ -135,7 +135,7 @@ This project was created by `Wenzel
 Jakob <http://rgl.epfl.ch/people/wjakob>`_. Significant features and/or
 improvements to the code were contributed by Jonas Adler, Lori A. Burns,
 Sylvain Corlay, Eric Cousineau, Aaron Gokaslan, Ralf Grosse-Kunstleve, Trent Houliston, Axel
-Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov Johan Mabille, Tomasz Miąsko,
+Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov, Johan Mabille, Tomasz Miąsko,
 Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling, Pim
 Schellart, Henry Schreiner, Ivan Smirnov, Boris Staletic, and Patrick Stewart.