bpftool: Remove attach_type_name forward declaration

The attach_type_name definition was removed in commit 1ba5ad36
("bpftool: Use libbpf_bpf_attach_type_str"). Remove its forward
declaration in main.h as well.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220630093638.25916-1-tklauser@distanz.ch

tools/bpf/bpftool/main.h

@@ -63,8 +63,6 @@ static inline void *u64_to_ptr(__u64 ptr)
 #define HELP_SPEC_LINK							\
 	"LINK := { id LINK_ID | pinned FILE }"
 
-extern const char * const attach_type_name[__MAX_BPF_ATTACH_TYPE];
-
 /* keep in sync with the definition in skeleton/pid_iter.bpf.c */
 enum bpf_obj_type {
 	BPF_OBJ_UNKNOWN,