Improve the grammar in windows.rst (GH-1330)

Doc/using/windows.rst

@@ -550,9 +550,9 @@ Shebang Lines
 
 If the first line of a script file starts with ``#!``, it is known as a
 "shebang" line.  Linux and other Unix like operating systems have native
-support for such lines and are commonly used on such systems to indicate how
-a script should be executed.  This launcher allows the same facilities to be
-using with Python scripts on Windows and the examples above demonstrate their
+support for such lines and they are commonly used on such systems to indicate
+how a script should be executed.  This launcher allows the same facilities to
+be used with Python scripts on Windows and the examples above demonstrate their
 use.
 
 To allow shebang lines in Python scripts to be portable between Unix and