update github-actions

- updated `.github/workflows/ci.yaml` to use rust 1.78 instead of 1.62,
  since the llvm-tools change happened in 1.67.
- updated ubuntu 20.04 to 22.04
- updated actions/checkout from v2 to v4
- updated actions/cache from v1 to v4
- updated peaceiris/actions-gh-pages from v3 to v4

Author: gdamjan

.github/workflows/ci.yaml

@@ -7,37 +7,37 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
 
     continue-on-error: ${{ matrix.experimental || false }}
 
     strategy:
       matrix:
         rust:
-          - 1.62.0
+          - 1.78.0
           - nightly
         include:
           - rust: nightly
             experimental: true
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Install Rust
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
           toolchain: ${{ matrix.rust }}
           override: true
-          components: rustfmt, clippy, llvm-tools-preview
+          components: rustfmt, clippy, llvm-tools
           target: thumbv7m-none-eabi
 
       - name: Install Python dependencies
         run: |
           pip3 install --user python-dateutil linkchecker
 
       - name: Cache installed binaries
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         id: cache-bin
         with:
           path: ~/cache-bin
@@ -84,17 +84,17 @@ jobs:
           RUST_VERSION: ${{ matrix.rust }}
 
   deploy:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
 
     needs: [build]
 
     if: github.event_name == 'push' && github.ref == 'refs/heads/master'
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Cache installed binaries
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         id: cache-bin
         with:
           path: ~/cache-bin
@@ -107,7 +107,7 @@ jobs:
         run: mdbook build
 
       - name: Deploy book
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: book