fix: Remove default chrono dep on time for sqlx-cli

[TravisWhitehead]

TL;DR: Remove unnecessary dependency on time 0.1 in sqlx-cli; that version of time is deprecated and contains a vulnerability flagged by cargo audit.

Effects of Change: This change adjusts the feature flags configured for the chrono crate for sqlx-cli. It disables default features for chrono and enables the clock flag only. The outcome is that chrono will no longer include the default oldtime feature flag which removes the dependency on time.

Why? time 0.1 is deprecated and vulnerable to RUSTSEC-2020-0071. Although chrono's dependency on time is not actually vulnerable, it causes cargo audit to be noisey:

Crate:     time
Version:   0.1.44
Title:     Potential segfault in the time crate
Date:      2020-11-18
ID:        RUSTSEC-2020-0071
URL:       https://rustsec.org/advisories/RUSTSEC-2020-0071
Solution:  Upgrade to >=0.2.23
Dependency tree:
time 0.1.44
└── chrono 0.4.19
    ├── sqlx-core 0.6.1
    │   ├── sqlx-macros 0.6.1
    │   │   └── sqlx 0.6.1
    │   │       ├── sqlx-test 0.1.0
    │   │       │   └── sqlx 0.6.1
    │   │       ├── sqlx-example-sqlite-todos 0.1.0
    │   │       ├── sqlx-example-postgres-transaction 0.1.0
    │   │       ├── sqlx-example-postgres-todos 0.1.0
    │   │       ├── sqlx-example-postgres-mockable-todos 0.1.0
    │   │       ├── sqlx-example-postgres-listen 0.1.0
    │   │       ├── sqlx-example-postgres-axum-social 0.1.0
    │   │       ├── sqlx-example-mysql-todos 0.1.0
    │   │       ├── sqlx-core 0.6.1
    │   │       ├── sqlx-cli 0.6.1
    │   │       ├── sqlx-bench 0.1.0
    │   │       ├── json 0.1.0
    │   │       └── files 0.1.0
    │   └── sqlx 0.6.1
    ├── sqlx-cli 0.6.1
    ├── sqlx-bench 0.1.0
    └── serde_with 2.0.0
        └── sqlx-example-postgres-axum-social 0.1.0

Unfortunately chrono 0.4.19 also generates noise with cargo audit, but 🤷

[jhpratt]

It's worth noting that chrono itself is vulnerable for the exact reason that time 0.1 is.