Logitech Media Server (Squeezebox) - upgrade to latest stable

[Hooverdan96]

The underlying docker structure has been adjusted to offer the latest stable build under the "latest" tag (has now entered the 8.x version). Replacing the current version 7.9.4 with a new one would be advisable. Based on past discussions, it should be introduced as a new one (especially, since the current specifies a version in its title, and the old one should be deprecated.

Adding additional information on how to continue to update/upgrade to the latest stable version, as the underlying container doesn't do it upon a stop/restart, like many of the ones that e.g. linuxserver.io offers.