doc: removing obsolete agent build instructions

Guile is no longer in contrib so this documentation is obsolete.

Change-Id: I884cf03b5d1fa677f6cf8036bd5b0dffec4dda88

doc/agent/build.rst

@@ -14,18 +14,6 @@ distributions.  If the required version is available on your distro, just
 install it using your distro's package manager. Development packages must be
 installed as well.
 
-Build Guile library
-===================
-
-To build Guile locally, you first need to enable it when building contrib, then
-recompile contrib::
-
-  cd daemon/contrib/native
-  ../bootstrap --enable-debug --enable-guile --enable-libunistring --enable-libffi --enable-libgc
-  make list
-  make fetch
-  make -j
-
 
 Compile
 =======