Update copyright year in macOS installer license copy (GH-17806)

(cherry picked from commit 32f1443)

Co-authored-by: Ned Deily <nad@python.org>

Mac/BuildScript/resources/License.rtf

@@ -1,5 +1,5 @@
-{\rtf1\ansi\ansicpg1252\cocoartf1671\cocoasubrtf600
-{\fonttbl\f0\fswiss\fcharset0 Helvetica-Bold;\f1\fswiss\fcharset0 Helvetica;\f2\fmodern\fcharset0 CourierNewPS-BoldMT;
+{\rtf1\ansi\ansicpg1252\cocoartf2511
+\cocoatextscaling0\cocoaplatform0{\fonttbl\f0\fswiss\fcharset0 Helvetica-Bold;\f1\fswiss\fcharset0 Helvetica;\f2\fmodern\fcharset0 CourierNewPS-BoldMT;
 \f3\fmodern\fcharset0 CourierNewPSMT;}
 {\colortbl;\red255\green255\blue255;}
 {\*\expandedcolortbl;;}
@@ -55,7 +55,7 @@ Thanks to the many outside volunteers who have worked under Guido's direction to
 \f1\b0 \
 1. This LICENSE AGREEMENT is between the Python Software Foundation ("PSF"), and the Individual or Organization ("Licensee") accessing and otherwise using this software ("Python") in source or binary form and its associated documentation.\
 \
-2. Subject to the terms and conditions of this License Agreement, PSF hereby grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce, analyze, test, perform and/or display publicly, prepare derivative works, distribute, and otherwise use Python alone or in any derivative version, provided, however, that PSF's License Agreement and PSF's notice of copyright, i.e., "Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019 Python Software Foundation; All Rights Reserved" are retained in Python alone or in any derivative version prepared by Licensee.\
+2. Subject to the terms and conditions of this License Agreement, PSF hereby grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce, analyze, test, perform and/or display publicly, prepare derivative works, distribute, and otherwise use Python alone or in any derivative version, provided, however, that PSF's License Agreement and PSF's notice of copyright, i.e., "Copyright \'a9 2001-2020 Python Software Foundation; All Rights Reserved" are retained in Python alone or in any derivative version prepared by Licensee.\
 \
 3. In the event Licensee prepares a derivative work that is based on or incorporates Python or any part thereof, and wants to make the derivative work available to others as provided herein, then Licensee hereby agrees to include in any such work a brief summary of the changes made to Python.\
 \