Update MSRV for lints.

.github/workflows/lints.yml

@@ -70,19 +70,19 @@ jobs:
         if: always()
 
   rust-clippy:
-    name: Clippy (1.54.0)
+    name: Clippy (1.56.1)
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.54.0
+          toolchain: 1.56.1
           components: clippy
           override: true
       - name: Run clippy
         uses: actions-rs/clippy-check@v1
         with:
-          name: Clippy (1.54.0)
+          name: Clippy (1.56.1)
           token: ${{ secrets.GITHUB_TOKEN }}
           args: --all-features --all-targets -- -D warnings
 
@@ -93,7 +93,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.54.0
+          toolchain: 1.56.1
           override: true
       - run: rustup component add rustfmt
       - uses: actions-rs/cargo@v1