set minimum compiler version to 1.56 (version 2021)

Author: sander2

.github/workflows/rust.yml

@@ -15,7 +15,7 @@ jobs:
                     - rust: nightly
                       env:
                           RUSTFMTCHK: false
-                    - rust: 1.41.1
+                    - rust: 1.56.0
                       env:
                           RUSTFMTCHK: false
         steps:
@@ -27,7 +27,6 @@ jobs:
                   profile: minimal
                   toolchain: ${{ matrix.rust }}
                   override: true
-            - run: cargo update -p serde --precise 1.0.189
             - name: Running test script
               env: ${{ matrix.env }}
               run: ./contrib/test.sh

README.md

@@ -47,4 +47,4 @@ The following versions are officially supported and automatically tested:
 * 0.21.0
 
 # Minimum Supported Rust Version (MSRV)
-This library should always compile with any combination of features on **Rust 1.41.1**.
+This library should always compile with any combination of features on **Rust 1.56.0** (the first compiler version that supported Rust version 2021).