Add changelog for 480
This MR was automatically created from CI, https://gitlab.com/gitlab-org/gitter/gitter-android-app/-/jobs/550389187
We moved CURRENT_VERSION.txt
-> 480.txt
This MR was automatically created from CI, https://gitlab.com/gitlab-org/gitter/gitter-android-app/-/jobs/550389187
We moved CURRENT_VERSION.txt
-> 480.txt