remove unused time features

[dimbleby]

leaving out std doesn't really do anything because formatting implies std per https://docs.rs/crate/time/0.3.0/features.

However local-offset is unused here, and since this is the feature that reintroduces thread-safety shenanigans it seems worthwhile to avoid it if we can.

It may be that what this really means is that the current implementation of timestamp_local() is in fact not doing anything to localise the timestamp, and that's a bug. I'm in the UTC timezone, so it's not quite straightforward for me to test this!

Edit: yeah, I'm pretty sure that there is no localisation going on. Probably what you really want is

-    let now: time::OffsetDateTime = std::time::SystemTime::now().into();
+    let now = time::OffsetDateTime::now_local();

the implementation of time::OffsetDateTime::now_utc() is exactly what you currently have in timestamp_local()

I'll submit a second MR and you can choose!

[Techcable]

Wow 👀

Good investigative work.....

[Techcable]

This is fine to merge right now. I don't think there is any risk....

I want to look at #44 more closely because

1. It triggers an "indeterminate offset" error both on my laptop and on Github
2. It addresses a very serious bug
   • However because of the error, I am not sure the solution works