Belatedly bump version number to 1.12.21 for development

Signed-off-by: Simon McVittie <smcv@collabora.com>
12 jobs for dbus-1.12 in 8 minutes and 55 seconds (queued for 14 seconds)
Name Stage Failure
failed
build:x86_64-w64-mingw32 Build
+ for pkg in expat-2.1.0-6 gcc-libs-5.2.0-4 gettext-0.19.6-1 glib2-2.46.1-1 libffi-3.2.1-3 zlib-1.2.8-9
+ wget http://repo.msys2.org/mingw/i686/mingw-w64-i686-expat-2.1.0-6-any.pkg.tar.xz
--2021-12-17 13:06:07-- http://repo.msys2.org/mingw/i686/mingw-w64-i686-expat-2.1.0-6-any.pkg.tar.xz
Resolving repo.msys2.org (repo.msys2.org)... 178.63.98.68
Connecting to repo.msys2.org (repo.msys2.org)|178.63.98.68|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2021-12-17 13:06:08 ERROR 404: Not Found.

Cleaning up file based variables
ERROR: Job failed: exit code 1
failed
build:i686-w64-mingw32-debug Build
+ for pkg in expat-2.1.0-6 gcc-libs-5.2.0-4 gettext-0.19.6-1 glib2-2.46.1-1 libffi-3.2.1-3 zlib-1.2.8-9
+ wget http://repo.msys2.org/mingw/i686/mingw-w64-i686-expat-2.1.0-6-any.pkg.tar.xz
--2021-12-17 13:06:13-- http://repo.msys2.org/mingw/i686/mingw-w64-i686-expat-2.1.0-6-any.pkg.tar.xz
Resolving repo.msys2.org (repo.msys2.org)... 178.63.98.68
Connecting to repo.msys2.org (repo.msys2.org)|178.63.98.68|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2021-12-17 13:06:13 ERROR 404: Not Found.

Cleaning up file based variables
ERROR: Job failed: exit code 1