Update MSRV to 1.56

.github/workflows/ci.yml

@@ -7,16 +7,16 @@ jobs:
     runs-on: ubuntu-latest
     env:
       # work-around https://github.com/rust-lang/cargo/issues/10303
-      CARGO_NET_GIT_FETCH_WITH_CLI: ${{ matrix.rust == '1.45.0' }}
+      CARGO_NET_GIT_FETCH_WITH_CLI: ${{ matrix.rust == '1.56.0' }}
     strategy:
       matrix:
         rust:
-          - 1.45.0
+          - 1.56.0
           - stable
           - beta
           - nightly
         include:
-          - rust: 1.45.0
+          - rust: 1.56.0
             test_features: "--features impl_json_schema"
             allow_failure: false
           - rust: stable
@@ -36,9 +36,6 @@ jobs:
           profile: minimal
           toolchain: ${{ matrix.rust }}
           override: true
-      - if: matrix.rust == '1.45.0'
-        # work-around https://github.com/serde-rs/serde/issues/2255 and similar crate/rustc compatibility issues
-        run: cargo update -p serde --precise 1.0.142 && cargo update -p once_cell --precise 1.10.0 && cargo update -p pretty_assertions --precise 1.2.1 && cargo update -p trybuild --precise 1.0.64
       - name: Check with no feature flags
         run: cargo check --verbose --no-default-features
         continue-on-error: ${{ matrix.allow_failure }}