Upgrade `golang.org/x/sys` from `v0.17.0` to `v0.21.0`

[daniel-weisse]

v0.20.0 of golang.org/x/sys renamed XDPUmemReg.Size to XDPUmemReg.Chunk_size.

Since gvisor makes use of XDPUmemReg, projects with gvisor as a Go dependency can't upgrade golang.org/x/sys until the dependency is upgraded.

Changeset was created using the following

git checkout origin/go
go get golang.org/x/[email protected]
git checkout <my-branch>
bazel run //:gazelle -- update-repos -from_file=go.mod
<Update XDPUmemReg.Size to XDPUmemReg.Chunk_size>