Update MSRV to 1.74, to match what our deps actually require

We actually already required much higher than 1.56 on master,
(some dependency updates effectively bumped it, but weren't accounted for)

Author: tux3

Cargo.toml

@@ -3,7 +3,7 @@ name = "armerge"
 version = "2.2.0"
 authors = ["tux3 <[email protected]>"]
 edition = "2021"
-rust-version = "1.56"
+rust-version = "1.74"
 license = "MIT OR Apache-2.0"
 readme = "README.md"
 repository = "https://github.com/tux3/armerge/"

README.md

@@ -2,7 +2,7 @@
 
 [![crates.io](https://img.shields.io/crates/v/armerge.svg)](https://crates.io/crates/armerge)
 [![Apache 2 licensed](https://img.shields.io/badge/license-Apache%202-blue)](./LICENSE)
-![MSRV](https://img.shields.io/badge/MSRV-1.56-informational)
+![MSRV](https://img.shields.io/badge/MSRV-1.74-informational)
 [![CI](https://github.com/tux3/armerge/workflows/CI/badge.svg)](https://github.com/tux3/armerge/actions?query=workflow%3ACI)
 
 You can use armerge to combine multiple static libraries into a single merged `ar` archive.