msrv: bump to 1.63 (#708)

* ci: only check h2 package for msrv
* msrv: bump to 1.63, tokio requires it

Author: seanmonstar

.github/workflows/CI.yml

@@ -93,4 +93,4 @@ jobs:
         with:
           toolchain: ${{ steps.metadata.outputs.msrv }}
 
-      - run: cargo check
+      - run: cargo check -p h2

Cargo.toml

@@ -19,7 +19,7 @@ keywords = ["http", "async", "non-blocking"]
 categories = ["asynchronous", "web-programming", "network-programming"]
 exclude = ["fixtures/**", "ci/**"]
 edition = "2018"
-rust-version = "1.56"
+rust-version = "1.63"
 
 [features]
 # Enables `futures::Stream` implementations for various types.