build: unstable release version bump to 1.21.5
diff --git a/meson.build b/meson.build
index 00d391b..12b4fa6 100644
--- a/meson.build
+++ b/meson.build
@@ -3,7 +3,7 @@
 
 project(
   'ModemManager', 'c',
-  version: '1.21.4',
+  version: '1.21.5',
   license: 'GPL2',
   default_options: [
     'buildtype=debugoptimized',