[nfcd] Avoid plugin overlinking. JB#48413

Even though plugins would almost certainly have to link with glib-2.0
there's no reason for that to be a strict requirement.

core/nfcd-plugin.pc.in

@@ -4,5 +4,5 @@ includedir=/usr/include
 Name: ${name}
 Description: Header files for building ${name} plugins
 Version: @version@
-Requires: glib-2.0
+Requires.private: glib-2.0
 Cflags: -I${includedir} -I${includedir}/${name}