Upgrade go to latest patch release

[jmhbnz]

What would you like to be added?

A new go patch release has been published:

• go1.21.4 (released 2023-11-07) includes security fixes to the path/filepath package, as well as bug fixes to the linker, the runtime, the compiler, and the go/types, net/http, and runtime/cgo packages. See the Go 1.21.4 milestone on our issue tracker for details.

We should update to this version by bumping the version in .go-version file in the main branch.

Once the changes have been merged in main we should also raise pull requests for release-3.5 and release-3.4 branches as well to update those branches to 1.20.11 so the fixes can make it into our next patch releases.

Completion tracking

• main - etcd: upgrade go version from 1.21.3 to 1.21.4 #16895
• release-3.5 [3.5] etcd: upgrade go version from 1.20.10 to 1.20.11 #16915
• release-3.4 [3.4] etcd: upgrade go version from 1.20.10 to 1.20.11 #16916
• etcd-io/bbolt master etcd: upgrade go version from 1.21.4 bbolt#607
• etcd-io/raft main etcd: upgrade go version from 1.21.3 to 1.21.4 raft#109

Why is this needed?

Keep etcd projects up to date with the latest patch releases and incorporate the latest security updates.

[arjunmalhotra1]

Hey @jmhbnz!
I would be interested in taking this up as my contribfest issue.

[ahrtr]

It's breaking the workflow check and blocking other PRs, let's get this fixed & merged asap.

[vivekpatani]

@jmhbnz any plans to back port to 3.5.x as well? If needed help with that, can do.
CC: @ahrtr @serathius

[jmhbnz]

@jmhbnz any plans to back port to 3.5.x as well? If needed help with that, can do.

Certainly are - refer my comment in #16895 (comment). I believe @arjunmalhotra1 will be raising the backports. However we also should be raising updates for both etcd-io/bbolt and etcd-io/raft so feel free to work on those! 🙏🏻

[ahrtr]

Please update the changelog for 3.4 and 3.5 as well, thanks.