rtpengine: Makefile - remove internal libs compilation and linking

- libs are compiled in the core

src/modules/rtpengine/Makefile

@@ -5,7 +5,4 @@ auto_gen=
 NAME=rtpengine.so
 LIBS=
 
-SERLIBPATH=../../lib
-SER_LIBS+=$(SERLIBPATH)/srdb1/srdb1
 include ../../Makefile.modules
-