remove oldtime feature from chrono dependency

[syphar]

I checked why after #1963 we still have a dependency to time@0.1.

Chrono actually tried to stay backwards-compatible and introduced an oldtime feature, which is default.

Removing it also removes the depdency to the old time crate.

Checking the other dependencies:

$ cargo tree -i time@0.1.45
time v0.1.45
├── chrono v0.4.23
│   ├── aws-smithy-types-convert v0.51.0
│   │   └── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
│   ├── chrono-tz v0.6.3
│   │   └── tera v1.17.1
│   │       └── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
│   ├── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
│   ├── postgres-types v0.2.4
│   │   ├── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
│   │   └── tokio-postgres v0.7.7
│   │       └── postgres v0.19.4
│   │           ├── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
│   │           ├── r2d2_postgres v0.18.1
│   │           │   └── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
│   │           └── schemamama_postgres v0.3.0
│   │               └── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
│   └── tera v1.17.1 (*)
├── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
└── hyper v0.10.16
    └── iron v0.6.1
        ├── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)
        └── router v0.6.0
            └── docs-rs v0.6.0 (/Users/syphar/src/rust-lang/docs.rs)

They all changed to dropping the oldtime feature in recent releases.

So when this PRs is merged, and these:

• upgrade procfs dependency #1971
• upgrade AWS SDKs #1970
• migrate the main rustdoc handlers to axum, drop iron #1963

then we can drop the audit-ignore for the time and chrono localtime_r rustsec entries.