.gitmodules: Remove ftl-sdk submodule

.gitmodules

@@ -4,9 +4,6 @@
 [submodule "plugins/obs-browser"]
 	path = plugins/obs-browser
 	url = https://github.com/obsproject/obs-browser.git
-[submodule "plugins/obs-outputs/ftl-sdk"]
-	path = plugins/obs-outputs/ftl-sdk
-	url = https://github.com/Mixer/ftl-sdk.git
 [submodule "plugins/obs-websocket"]
 	path = plugins/obs-websocket
 	url = https://github.com/obsproject/obs-websocket.git