Fix opam files (backports from the 13.0 opam release)

Context

In the Octez 13.0 opam release, @pirbo and the opam reviewer had to make some fixes to the .opam files. This MR backport those fixes to the manifest.

Manually testing the MR

You can run git log -p -- opam and check that the diff matches the 3 patches that were added to https://github.com/ocaml/opam-repository/pull/21394/commits:

a248d11dca Update packages/tezos-proxy-server-config/tezos-proxy-server-config.13.0/opam
520d89e637 Update packages/tezos-lwt-result-stdlib/tezos-lwt-result-stdlib.13.0/opam
c52a18b608 Missing bits to upstream in tezos/tezos

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR