generic: drop extra-old-deprecated pending fix patch for sch codel

generic: drop extra-old-deprecated pending fix patch for sch codel

Patch 620-net_sched-codel-do-not-defer-queue-length-update.patch is
actually an ancient patch that somehow manage to be ported for 7 solid
years.

This comes from [1] where a fix patch was proposed. Nobody notice that
the proposed patch was actually rejected upstream in favor of [2]. And
the upstream fix patch is present in kernel from version 4.18.

This means that we were actually fixing for a non existant bug and maybe
introducing regression down the line.

Drop the patch for good as we already have a fix for it in flace for a
long time.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=109581
[2] https://github.com/torvalds/linux/commit/35b42da69e35536da603a50e40aa6c41b2f7b0f8

Signed-off-by: Christian Marangi <[email protected]>