Merge pull request #6484 from CaptV0rt3x/discord-rpc

update submodule discord-rpc to latest [now deprecated]

.gitmodules

@@ -18,7 +18,7 @@
 	url = https://github.com/libusb/libusb.git
 [submodule "discord-rpc"]
     path = externals/discord-rpc
-    url = https://github.com/discordapp/discord-rpc.git
+    url = https://github.com/discord/discord-rpc.git
 [submodule "Vulkan-Headers"]
     path = externals/Vulkan-Headers
     url = https://github.com/KhronosGroup/Vulkan-Headers.git