build(deps): bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/book.yml

@@ -9,7 +9,7 @@ jobs:
   deploy:
     runs-on: ubuntu-18.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@nightly
         id: toolchain
       - run: rustup override set ${{steps.toolchain.outputs.name}}

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
         os: [ubuntu-latest, windows-latest, macOS-latest]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Fetch path to Zcash parameters
         working-directory: ./zcash_proofs
         shell: bash
@@ -43,7 +43,7 @@ jobs:
           - wasm32-wasi
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Add target
         run: rustup target add ${{ matrix.target }}
       - run: cargo fetch
@@ -58,7 +58,7 @@ jobs:
     name: Bitrot check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       # Build benchmarks to prevent bitrot
       - name: Build benchmarks
         run: cargo build --all --benches
@@ -68,7 +68,7 @@ jobs:
     timeout-minutes: 30
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run clippy
         uses: actions-rs/clippy-check@v1
         with:
@@ -82,7 +82,7 @@ jobs:
     runs-on: ubuntu-latest
     continue-on-error: true
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@beta
         id: toolchain
       - run: rustup override set ${{steps.toolchain.outputs.name}}
@@ -102,7 +102,7 @@ jobs:
       options: --security-opt seccomp=unconfined
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Fetch path to Zcash parameters
         working-directory: ./zcash_proofs
         shell: bash
@@ -127,7 +127,7 @@ jobs:
     name: Intra-doc links
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: cargo fetch
       # Requires #![deny(rustdoc::broken_intra_doc_links)] in crates.
       - name: Check intra-doc links
@@ -138,6 +138,6 @@ jobs:
     timeout-minutes: 30
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Check formatting
         run: cargo fmt --all -- --check