Update "make" command argument

"config" is not a valid argument for the "make" command when dealing with dahdi-linux-complete-3.4.0+3.4.0 (according to its makefile)

Author: YngProgrammer

docs/Getting-Started/Installing-Asterisk/Installing-Asterisk-From-Source/Prerequisites/Building-and-Installing-DAHDI.md

@@ -44,7 +44,7 @@ Starting with DAHDI-Linux-complete version 2.8.0+2.8.0, all files necessary to i
 
 [root@server dahdi-linux-complete-2.X.Y+2.X.Y]# make install
 
-[root@server dahdi-linux-complete-2.X.Y+2.X.Y]# make config 
+[root@server dahdi-linux-complete-2.X.Y+2.X.Y]# make install-config
 
 ```