Deprecated from_timestamp method used in example for DateTime

[greg-el]

The example given in https://docs.rs/chrono/latest/chrono/struct.DateTime.html#example appears to use the deprecated from_timestamp:

warning: use of deprecated associated function `chrono::NaiveDateTime::from_timestamp`: use `from_timestamp_opt()` instead
  --> src/main.rs:60:60
   |
60 |             date: DateTime::<Utc>::from_utc(NaiveDateTime::from_timestamp(61, 0), Utc),
   |                                                            ^^^^^^^^^^^^^^
   |
   = note: `#[warn(deprecated)]` on by default

I figure this should be as simple as replacing NaiveDateTime::from_timestamp(61, 0) with NaiveDateTime::from_timestamp_opt(61, 0).unwrap(), happy to open a PR to do so!

[djc]

Would be great to have a PR for this! Be sure to target the 0.4.x branch, thanks!

[pitdicker]

This issue is fixed by #939.