Remove Google Play Music Desktop Player

I no longer use this application, and the move to YouTube Music leaves
its future uncertain.

README.md

 - [Closure Compiler](https://developers.google.com/closure/compiler/) v20200614 ([GitHub releases](https://github.com/google/closure-compiler/releases))
 - [Dual Key Remap](https://github.com/ililim/dual-key-remap) v0.5 ([GitHub releases](https://github.com/ililim/dual-key-remap/releases))
 - [Go Replace](https://github.com/piranha/goreplace) v2.5 ([GitHub releases](https://github.com/piranha/goreplace/releases))
-- [Google Play Music Desktop Player](https://www.googleplaymusicdesktopplayer.com/) v4.7.1 ([GitHub releases](https://github.com/MarshallOfSound/Google-Play-Music-Desktop-Player-UNOFFICIAL-/releases))
 - [hledger](https://hledger.org/) v1.18.1 ([Downloads](https://hledger.org/download.html), [GitHub releases](https://github.com/simonmichael/hledger/releases))
 - [Multiscreen Blank](http://multiscreenblank.nookkin.com/) v2.4.0.0 ([Releases](http://dl.nookkin.com/products/multiscreenblank/))
 - [scc](https://github.com/boyter/scc) v3.0.0 ([GitHub releases](https://github.com/boyter/scc/releases))

bucket/gpmdp.json

-{
-	"homepage": "https://www.googleplaymusicdesktopplayer.com/",
-	"description": "A beautiful cross platform Desktop Player for Google Play Music",
-	"version": "4.7.1",
-	"license": "MIT",
-	"url": "https://github.com/MarshallOfSound/Google-Play-Music-Desktop-Player-UNOFFICIAL-/releases/download/v4.7.1/GPMDP_3-4.7.1-full.nupkg#/dl.7z",
-	"hash": "sha256:D865DFD7C4C4CD62EBEA40230E79EEA0D957E333733047A10053FB1D44A12FD9",
-	"extract_dir": "lib/net45",
-	"shortcuts": [
-		[
-			"Google%20Play%20Music%20Desktop%20Player.exe",
-			"Google Play Music Desktop Player (GPMDP)"
-		]
-	],
-	"checkver": {
-		"github": "https://github.com/MarshallOfSound/Google-Play-Music-Desktop-Player-UNOFFICIAL-"
-	}
-}