build: remove llvm-dev dependency from libbcc

In iovisor#4737 I added depedency on llvm-config.h in order to discover what LLVM version
is being used. This was only meant to be used at build time.
By adding llvm-config.h in bpf_module.h, a public header of libbcc, I introduced
a dependency on llvm-dev to libbcc which is unnecessary.

This change removes the include from `bpf_module.h`, which should be enough.

It does not seem I need to add the include in any other files.

Fixes iovisor#4997

Signed-off-by: Manu Bretelle <chantr4@gmail.com>

src/cc/bpf_module.h

@@ -22,8 +22,6 @@
 #include <string>
 #include <vector>
 
-#include <llvm/Config/llvm-config.h>
-
 #include "bcc_exception.h"
 #include "table_storage.h"