obs-outputs: Drop unused config file

The obs-outputs-config.h.in file is not actually used. It only
defines the FTL_FOUND variable, but the build system takes care
of that by setting a compiler argument for that.

Drop that file.

plugins/obs-outputs/obs-outputs-config.h.in

@@ -1,15 +0,0 @@
-#pragma once
-
-#ifndef TRUE
-#define TRUE 1
-#endif
-
-#ifndef ON
-#define ON 1
-#endif
-
-#ifndef FALSE
-#define FALSE 0
-#endif
-
-#cmakedefine FTL_FOUND