[PATCH] doc: fix missing title underline

[Zhang, Qi Z]

> -----Original Message-----
> From: Kevin Liu <kevinx.liu at intel.com>
> Sent: Tuesday, July 5, 2022 6:42 PM
> To: dev at dpdk.org
> Cc: Xing, Beilei <beilei.xing at intel.com>; Zhang, Yuying
> <yuying.zhang at intel.com>; Liu, KevinX <kevinx.liu at intel.com>
> Subject: [PATCH] doc: fix missing title underline
> 
> Title underline too short. Fill title underline.
> 
> Fixes: ae97b8b89826 ("net/i40e: fix error disable double VLAN")

The patch has been squashed to above commit in dpdk-next-net-intel.