Fix API coverage version in README: "0.5.1" => "5.1"
<img src="https://img.shields.io/badge/license-MIT-blue.svg">
</a>
<a href="https://core.telegram.org/bots/api">
- <img src="https://img.shields.io/badge/API%20coverage-Up%20to%200.5.1%20(inclusively)-green.svg">
+ <img src="https://img.shields.io/badge/API%20coverage-Up%20to%205.1%20(inclusively)-green.svg">
</a>
<a href="https://crates.io/crates/teloxide_core">
<img src="https://img.shields.io/crates/v/teloxide_core.svg">
