fix: update sigstore/cosign-installer to v4

Author: lukashankeln

.github/workflows/build-multiarch.yml

@@ -319,7 +319,7 @@ jobs:
 
       - name: Install cosign
         if: inputs.sign_image
-        uses: sigstore/cosign-installer@3454372f43399081ed03b604cb2d021dabca52bb # v3.8.2
+        uses: sigstore/cosign-installer@faadad0cce49287aee09b3a48701e75088a2c6ad # v4.0.0
 
       - name: Sign image
         if: inputs.sign_image