Bump MSRV for newer tokio versions

Author: djc

.github/workflows/CI.yml

@@ -87,6 +87,6 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: "1.63"
+          toolchain: "1.70"
 
       - run: cargo check --locked --lib --all-features

Cargo.toml

@@ -9,7 +9,7 @@ readme = "README.md"
 description = "Asynchronous TLS/SSL streams for Tokio using Rustls."
 categories = ["asynchronous", "cryptography", "network-programming"]
 edition = "2021"
-rust-version = "1.63"
+rust-version = "1.70"
 exclude = ["/.github", "/examples", "/scripts"]
 
 [dependencies]