bpftool: Fix prog object type in manpage

bpftool's man page lists "program" as one of possible values for OBJECT,
while in fact bpftool accepts "prog" instead.

Reported-by: Jerry Snitselaar <[e-mail]>
Signed-off-by: Artem Savkov <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Acked-by: Yonghong Song <[e-mail]>
Acked-by: Quentin Monnet <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/bpf/bpftool/Documentation/bpftool.rst

···
 
 	**bpftool** **version**
 
-	*OBJECT* := { **map** | **program** | **link** | **cgroup** | **perf** | **net** | **feature** |
+	*OBJECT* := { **map** | **prog** | **link** | **cgroup** | **perf** | **net** | **feature** |
 	**btf** | **gen** | **struct_ops** | **iter** }
 
 	*OPTIONS* := { { **-V** | **--version** } | |COMMON_OPTIONS| }