Bump MoonDeck to 1.6.15

[FrogTheFrog]

MoonDeck

• Activated host selection dropdown even when there is only 1 host in QAM, so that the navigation is less broken.
• Added a setting for a custom Moonlight executable (AppImage or whatever).

Checklist:

Developer Checklist

• I am the original author or an authorized maintainer of this plugin.
• I have abided by the licenses of the libraries I am utilizing, including attaching license notices where appropriate.

Plugin Checklist

• I have verified that my plugin works properly on the Stable and Beta update channels of SteamOS.
• I have verified my plugin is unique or alternatively provides more/alternative functionality to a similar plugin already on the store.

Plugin Backend Checklist

• No: I am using a custom backend other than Python.
• No: I am using a tool or software from a 3rd party FOSS project that does not have it's dependencies statically linked.
• No: I am using a custom binary that has all of it's dependencies statically linked.

Testing

• Tested on SteamOS Stable/Beta Update Channel.

[TrainDoctor]

Changes look good, off to testing.

[nabel0]

Tested and works perfect on SteamOS Stable/Beta Update Channel.
Tried out using the latest nightly Appimage of Moonlight. and works fine
As usual awesome sauce...Thnx @FrogTheFrog