doc: remove repeated repeated words

doc: remove repeated repeated words

Some duplicate words were detected with a script.

Fixes: fdec9301f52d ("doc: add flow classify guides")
Fixes: 4dc6d8e63c16 ("doc: add graph library guide")
Fixes: 30d3aa861db5 ("doc: rework VM power manager user guide")
Fixes: 0d547ed03717 ("examples/ipsec-secgw: support configuration file")
Fixes: e64833f2273a ("examples/l2fwd-keepalive: add sample application")
Cc: stable@dpdk.org
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: David Marchand <david.marchand@redhat.com>