increase MSRV to 1.56.1

.github/workflows/test.yml

@@ -69,7 +69,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        toolchain: ["1.48.0", "stable", "nightly"]
+        toolchain: ["1.56.1", "stable", "nightly"]
 
     steps:
       - uses: actions/checkout@v3
@@ -79,17 +79,6 @@ jobs:
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.toolchain }}
-      - run: |
-          cargo update
-          cargo update -p which --precise 4.2.5
-          cargo update -p tempfile --precise 3.3.0
-          cargo update -p log --precise 0.4.18
-          cargo update -p serde_json --precise 1.0.99
-          cargo update -p serde --precise 1.0.156
-          cargo update -p regex --precise 1.7.3
-          cargo update -p quote --precise 1.0.28
-          cargo update -p proc-macro2 --precise 1.0.63
-        if: ${{ matrix.toolchain == '1.48.0' }}
       - run: cargo build
 
   build-nix: