nixos/version: remove strict type constraints from image options

This constraints aren't super useful because they arent really enforced
by the software, so it's hard to get them right and we've gotten them
wrong multiple times in the past. It's better to remove them altogether
in the spirit of RFC 42.

nixos/modules/misc/version.nix

@@ -121,7 +121,7 @@ in
     image = {
 
       id = lib.mkOption {
-        type = types.nullOr (types.strMatching "^[a-z0-9._-]+$");
+        type = types.nullOr types.str;
         default = null;
         description = ''
           Image identifier.
@@ -135,7 +135,7 @@ in
       };
 
       version = lib.mkOption {
-        type = types.nullOr (types.strMatching "^[a-z0-9._-~^]+$");
+        type = types.nullOr types.str;
         default = null;
         description = ''
           Image version.