[newlib-cygwin] doc: Also update shebang for chapter-texi2docbook.py

[Jon TURNEY]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=ed1573fc178fa1534ade5306f8bcef707ea346d0

commit ed1573fc178fa1534ade5306f8bcef707ea346d0
Author: Jon Turney <jon.turney@dronecode.org.uk>
Date:   Tue Aug 25 17:16:36 2020 +0100

    doc: Also update shebang for chapter-texi2docbook.py

Diff:
---
 newlib/doc/chapter-texi2docbook.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/newlib/doc/chapter-texi2docbook.py b/newlib/doc/chapter-texi2docbook.py
index e21489b9a..1a7803091 100755
--- a/newlib/doc/chapter-texi2docbook.py
+++ b/newlib/doc/chapter-texi2docbook.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # python script to convert the handwritten chapter .texi files, which include
 # the generated files for each function, to DocBook XML