bpo-32430: Rename Modules/Setup.dist to Modules/Setup (GH-8229)

bpo-32430: Rename Modules/Setup.dist to Modules/Setup

Remove the necessity to copy the former manually to the latter when updating the local source tree.
diff --git a/Modules/makesetup b/Modules/makesetup
index 020b199..c7b0a60 100755
--- a/Modules/makesetup
+++ b/Modules/makesetup
@@ -17,7 +17,7 @@
 # Setup files after a -n option are used for their variables, modules
 # and libraries but not for their .o files.
 #
-# See Setup.dist for a description of the format of the Setup file.
+# See Setup for a description of the format of the Setup file.
 #
 # The following edits are made:
 #