chore: bump version to 2.0.4

update changelog to 2.0.4

Author: wjyrich

debian/changelog

@@ -1,3 +1,9 @@
+dde-session (2.0.4) unstable; urgency=medium
+
+  * Release 2.0.4
+
+ -- WuJiangYu <wujiangyu@uniontech.com>  Thu, 03 Jul 2025 17:13:14 +0800
+
 dde-session (2.0.3) unstable; urgency=medium
 
   * fix: update systemd service configurations