Update macOS installer displays for 2.7.17rc1 (#16634)

Mac/BuildScript/resources/ReadMe.rtf

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+{\rtf1\ansi\ansicpg1252\cocoartf1671\cocoasubrtf600
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 {\colortbl;\red255\green255\blue255;}
@@ -8,6 +8,13 @@
 
 \f0\fs24 \cf0 This package will install Python $FULL_VERSION for macOS $MACOSX_DEPLOYMENT_TARGET for the following architecture(s): $ARCHITECTURES.\
 \
+\pard\tx720\tx1440\tx2160\tx2880\tx3600\tx4320\tx5040\tx5760\tx6480\tx7200\tx7920\tx8640\partightenfactor0
+
+\f1\b \cf0 NOTE: 
+\f0\b0 This is the release candidate for Python 2.7.17.  Any updates needed to support the latest release of macOS, 
+\f1\b 10.15 Catalina,
+\f0\b0  will be provided after in 2.7.17 final.\
+\
 \pard\tx720\tx1440\tx2160\tx2880\tx3600\tx4320\tx5040\tx5760\tx6480\tx7200\tx7920\tx8640\pardirnatural\partightenfactor0
 
 \f1\b \cf0 \ul \ulc0 Which installer variant should I use? [CHANGED in 2.7.15]
@@ -63,7 +70,7 @@ As of 2.7.15, the 10.9+ installer variant comes with its own private version of
 \f0\b0 The 10.6+ variant now also uses a private version of Tcl/Tk 8.6.\
 \pard\tx720\tx1440\tx2160\tx2880\tx3600\tx4320\tx5040\tx5760\tx6480\tx7200\tx7920\tx8640\pardirnatural\partightenfactor0
 
-\f1\b \cf0 \ul \ulc0 \
+\f1\b \cf0 \ul \
 Binary installer support for Mac OS X 10.5 and earlier discontinued [CHANGED for Python 2.7.15]
 \f0\b0 \ulnone \
 \

Mac/BuildScript/resources/Welcome.rtf

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+{\rtf1\ansi\ansicpg1252\cocoartf1671\cocoasubrtf600
 \cocoascreenfonts1{\fonttbl\f0\fswiss\fcharset0 Helvetica;\f1\fswiss\fcharset0 Helvetica-Bold;\f2\fmodern\fcharset0 CourierNewPSMT;
 }
 {\colortbl;\red255\green255\blue255;}
@@ -30,4 +30,10 @@
 
 \f1\b CHANGED in 2.7.16:
 \f0\b0   the 10.6+ variant now also uses a built-in Tcl/Tk 8.6\
+\
+
+\f1\b NOTE: 
+\f0\b0 This is the release candidate for Python 2.7.17.  Any updates needed to support the latest release of macOS, 
+\f1\b 10.15 Catalina,
+\f0\b0  will be provided after in 2.7.17 final.\
 }
\ No newline at end of file