Use a `-dev` version in `meson.build`

This makes it obvious that this is a development release and also ensures since annotations don't look odd as the library version is lower than what's in meson.build

doc/libcmatrix.toml.in

 [library]
 version = "@VERSION@"
-description = "A matrix client client library written in GObjectified C"
+description = "A Matrix Client Library"
 authors = "Purism SPC"
 license = "LGPL-2.1-or-later"
 browse_url = "https://source.puri.sm/Librem5/libcmatrix"