remove use of NextRelease delimiter

Builds done on release tags (e.g. on travis) do not work because the
literal Changes file is copied from the release, which contains an extra
closing delimiter.

We could use an inc/ plugin to monkey-patch NextRelease to change its
delimiter (e.g. to triple braces), but that's pretty gross and liable to
cause confusion to future maintainers. Instead, let's just get edit out
the problematic content.

Author: karenetheridge

Changes

@@ -595,7 +595,7 @@ r1371 | schwern | 2003-04-06 03:52:59 -0500 (Sun, 06 Apr 2003) | 9 lines
 
  Fixing the ECHO macro on dmake.
 
- Fixing {{ '}'x2 }} escaping on dmake, but this is just a stopgap measure.
+ Fixing double-closing-brace escaping on dmake, but this is just a stopgap measure.
 
  Making ExtUtils::Manifest sort things case-insensitively.  I think it
  displays better.