mail-client/roundcube: remove unused file

Closes: https://github.com/gentoo/gentoo/pull/17539
Package-Manager: Portage-3.0.6, Repoman-3.0.1
Signed-off-by: Michael Mair-Keimberger <m.mairkeimberger@gmail.com>
Signed-off-by: Conrad Kostecki <conikost@gentoo.org>

mail-client/roundcube/files/POST-UPGRADE.txt

@@ -1,23 +0,0 @@
-Post-Upgrade Activities
------------------------
-1. Check .htaccess settings (some php settings could become required)
-2. If you're using the built-in addressbook, run indexing script:
-   ./bin/indexcontacts.sh.
-3. When upgrading from version older than 0.6-beta you should make sure your
-   folder settings contain a namespace prefix if necessary. For example Courier
-   users should add "INBOX." prefix to folder names in main configuration file.
-4. Check system requirements in INSTALL file.
-5. If you previously installed plugins through composer, update dependencies by
-   running:
-   php composer.phar self-update
-   php composer.phar update --no-dev
-6. Update your database and configurations by running:
-   ./bin/update.sh
-
-SQLite database upgrade
------------------------
-Versions older than 0.9 were supporting SQLite v2 only. Newer versions require
-database in v3 format. The best what you can do is to convert database file
-to the new format using command line tools:
-
-sqlite OLD.DB .dump | sqlite3 NEW.DB