Remove the unused `ScriptNameStripper.to_strip` in the FastCGI doc example.

Alernatively, `environ['SCRIPT_NAME'] = ''` should be replaced with something like:

    if environ['SCRIPT_NAME'].startswith(self.to_strip):
        environ['SCRIPT_NAME'] = environ['SCRIPT_NAME'][len(self.to_strip):]

docs/deploying/fastcgi.rst

@@ -95,8 +95,6 @@ Set yourapplication.fcgi::
     from yourapplication import app
 
     class ScriptNameStripper(object):
-       to_strip = '/yourapplication.fcgi'
-
        def __init__(self, app):
            self.app = app