* Use Http instead of CacheHttp

* Fix examples compiling

* Update MSRV lockfile

---------

Co-authored-by: GnomedDev <david2005thomas@gmail.com>

Before this commit, Poise compilation would fail with this error:

```
error[E0432]: unresolved import `crate::serenity`
  --> src/builtins/mod.rs:20:13
   |
20 | use crate::{serenity::CreateAllowedMentions, serenity_prelude as serenity, CreateReply};
   |             ^^^^^^^^
   |             |
   |             unresolved import
   |             help: a similar path exists: `crate::prefix_argument::key_value_args::serenity`

For more information about this error, try `rustc --explain E0432`.
error: could not compile `poise` (lib) due to 1 previous error
```