Bump actions/cache from 3 to 4 (#40)

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

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ipxe_build.yaml

@@ -18,7 +18,7 @@ jobs:
           fetch-depth: 0 # we need the entire history to build iPXE
 
       - name: Cache binaries
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: cache
         with:
           key: ipxe-x86-${{ env.IPXE_REF }}
@@ -47,7 +47,7 @@ jobs:
           fetch-depth: 0 # we need the entire history to build iPXE
 
       - name: Cache binaries
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: cache
         with:
           key: ipxe-arm32-${{ env.IPXE_REF }}
@@ -77,7 +77,7 @@ jobs:
           fetch-depth: 0 # we need the entire history to build iPXE
 
       - name: Cache binaries
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: cache
         with:
           key: ipxe-arm64-${{ env.IPXE_REF }}
@@ -104,22 +104,22 @@ jobs:
       - arm64
     steps:
       - name: Mount x86 cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           key: ipxe-x86-${{ env.IPXE_REF }}
           path:  |
             src/bin/*.kpxe
             src/bin*/*.efi
 
       - name: Mount arm32 cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           key: ipxe-arm32-${{ env.IPXE_REF }}
           path: |
             src/bin-arm32-efi/snponly.efi
 
       - name: Mount arm64 cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           key: ipxe-arm64-${{ env.IPXE_REF }}
           path: |