Up minimum socket2 to 0.6.0

Now that hyper-util uses `socket2::Socket::set_tcp_nodelay`, which was
added in [0.6.0]. It used to be called `socket2::Socket::set_nodelay` in
[0.5.10]. It also updates the MSRV to Rust 1.70 since that's the minimum
supported version in socket2 0.6.0.

[0.5.10]: https://docs.rs/socket2/0.5.10/socket2/struct.Socket.html#method.set_nodelay
[0.6.0]: https://docs.rs/socket2/0.6.0/socket2/struct.Socket.html#method.set_tcp_nodelay

Author: erickt

.github/workflows/CI.yml

@@ -60,7 +60,7 @@ jobs:
     needs: [style]
     strategy:
       matrix:
-        rust: [ 1.64 ] # keep in sync with 'rust-version' in Cargo.toml
+        rust: [ 1.70 ] # keep in sync with 'rust-version' in Cargo.toml
         os:
           - ubuntu-latest
           - windows-latest

Cargo.toml

@@ -11,7 +11,7 @@ authors = ["Sean McArthur <sean@seanmonstar.com>"]
 keywords = ["http", "hyper", "hyperium"]
 categories = ["network-programming", "web-programming::http-client", "web-programming::http-server"]
 edition = "2021"
-rust-version = "1.64"
+rust-version = "1.70"
 
 [package.metadata.docs.rs]
 features = ["full"]
@@ -29,7 +29,7 @@ ipnet = { version = "2.9", optional = true }
 libc = { version = "0.2", optional = true }
 percent-encoding = { version = "2.3", optional = true }
 pin-project-lite = "0.2.4"
-socket2 = { version = ">=0.5.9, <0.7", optional = true, features = ["all"] }
+socket2 = { version = ">=0.6.0, <0.7", optional = true, features = ["all"] }
 tracing = { version = "0.1", default-features = false, features = ["std"], optional = true }
 tokio = { version = "1", optional = true, default-features = false  }
 tower-layer = { version = "0.3", optional = true }