[libafl_cc] Remove duplicate FATAL preproc macro

`FATAL` is defined in the `common-llvm.h` and is therefore accessible to
all of the passes, remove the duplicate in the pass `.cc` file to remove
the compiler warning

Author: rchildre3

crates/libafl_cc/src/dump-cfg-pass.cc

@@ -38,13 +38,6 @@
 
 #include <nlohmann/json.hpp>
 
-#define FATAL(x...)               \
-  do {                            \
-    fprintf(stderr, "FATAL: " x); \
-    exit(1);                      \
-                                  \
-  } while (0)
-
 using namespace llvm;
 
 namespace {