[ci] Update action versions to silence GitHub warnings

Signed-off-by: Michael Brown <mcb30@ipxe.org>

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
         run: |
           sudo chown $(id -un) /var/cache/apt/archives
       - name: Cache packages
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: /var/cache/apt/archives/*.deb
           key: apt-cache-${{ github.run_id }}-${{ github.run_attempt }}
@@ -32,14 +32,14 @@ jobs:
     needs: cache
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Cache permissions
         run: |
           sudo chown $(id -un) /var/cache/apt/archives
       - name: Cache packages
-        uses: actions/cache/restore@v3
+        uses: actions/cache/restore@v4
         with:
           path: /var/cache/apt/archives/*.deb
           key: apt-cache-${{ github.run_id }}-${{ github.run_attempt }}
@@ -68,14 +68,14 @@ jobs:
     needs: cache
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Cache permissions
         run: |
           sudo chown $(id -un) /var/cache/apt/archives
       - name: Cache packages
-        uses: actions/cache/restore@v3
+        uses: actions/cache/restore@v4
         with:
           path: /var/cache/apt/archives/*.deb
           key: apt-cache-${{ github.run_id }}-${{ github.run_attempt }}
@@ -97,14 +97,14 @@ jobs:
     needs: cache
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Cache permissions
         run: |
           sudo chown $(id -un) /var/cache/apt/archives
       - name: Cache packages
-        uses: actions/cache/restore@v3
+        uses: actions/cache/restore@v4
         with:
           path: /var/cache/apt/archives/*.deb
           key: apt-cache-${{ github.run_id }}-${{ github.run_attempt }}

.github/workflows/coverity.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Download Coverity Scan
         run: |
           curl --form token=${{ secrets.COVERITY_SCAN_TOKEN }} \