bpftool: Fix typos

Fix typos in documentation.

Reported-by: Matthew Wilcox <[e-mail]>
Reported-by: Quentin Monnet <[e-mail]>
Signed-off-by: Andrew Kreimer <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Acked-by: Quentin Monnet <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/bpf/bpftool/Documentation/bpftool-gen.rst

···
     CO-RE based application, turning the application portable to different
     kernel versions.
 
-    Check examples bellow for more information how to use it.
+    Check examples below for more information on how to use it.
 
 bpftool gen help
     Print short help message.