docs: document hyper dependency as a workaround for a2 bug

[link2xt]

No description provided.

[link2xt]

If I remove dependency, I get these failures:

Apr 14 23:05:27 page systemd[1]: Started notifications.service - Notification Service.
Apr 14 23:05:27 page notifiers[398104]: {"level":30,"time":1713135927946,"msg":"14968 devices registered currently"}
Apr 14 23:05:27 page notifiers[398104]: {"level":30,"time":1713135927947,"msg":"Listening on 127.0.0.1:port"}
Apr 14 23:05:27 page notifiers[398104]: {"level":30,"time":1713135927947,"msg":"Server listening on http://127.0.0.1:9000"}
Apr 14 23:05:27 page notifiers[398104]: {"level":30,"time":1713135927947,"msg":"Waking up devices every 20m"}
Apr 14 23:05:27 page notifiers[398104]: {"level":30,"time":1713135927960,"msg":"sending notifications to 14968 devices"}
Apr 14 23:05:27 page notifiers[398104]: {"level":30,"time":1713135927960,"msg":"notify: 0004d9d154b32c2a96c75d3bb26261d70d8daae96849c6bdc5d65988b62cf415"}
Apr 14 23:05:28 page notifiers[398104]: thread 'async-std/runtime' panicked at 'executor must be set', /home/notifications/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hyper-0.14.27/src/common/exec.rs:>
Apr 14 23:05:28 page notifiers[398104]: note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Apr 14 23:05:28 page notifiers[398104]: thread 'main' panicked at 'task has failed', /home/notifications/.cargo/registry/src/index.crates.io-6f17d22bba15001f/async-task-4.4.0/src/task.rs:452:45
Apr 14 23:05:28 page systemd[1]: notifications.service: Main process exited, code=exited, status=101/n/a

[link2xt]

Apparently there is an upstream fix: WalletConnect/a2#77