ci(deps): Update cosign

It seems that cosign has moved to a new format by default (in v3.x).
Since we are not using harbor, but ghcr.io, it seems we can update to
v3.x.

Signed-off-by: Anastassios Nanos <ananos@nubificus.co.uk>

Author: ananos

.github/workflows/build-latest.yml

@@ -129,7 +129,7 @@ jobs:
           jq -r '.[0].Id')" >> $GITHUB_ENV
 
       - name: Install cosign
-        uses: sigstore/cosign-installer@d58896d6a1865668819e1d91763c7751a165e159 # main
+        uses: sigstore/cosign-installer@faadad0cce49287aee09b3a48701e75088a2c6ad # main (v3)
 
       - name: Sign the published Docker image
         env:
@@ -212,7 +212,7 @@ jobs:
           echo "manifest_sha=$VAR" >> "$GITHUB_OUTPUT"
 
       - name: Install cosign
-        uses: sigstore/cosign-installer@d58896d6a1865668819e1d91763c7751a165e159 # main
+        uses: sigstore/cosign-installer@faadad0cce49287aee09b3a48701e75088a2c6ad # main (v3)
 
       - name: Sign the published Docker image
         env: