Add ':' in thanks sections

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: jb2170

peps/pep-0786.rst

@@ -555,7 +555,7 @@ A pull request implementing this PEP is available on GitHub:
 Thanks
 ======
 
-Thank you to
+Thank you to:
 
 * Raymond Hettinger, for the initial suggestion of the two's complement behavior.