chore: upgrade cosign version (#465)

Signed-off-by: Batuhan Apaydın <batuhan.apaydin@trendyol.com>

.github/workflows/build.yml

@@ -32,7 +32,7 @@ jobs:
       - uses: actions/checkout@v2.3.5
       - uses: sigstore/cosign-installer@main
         with:
-          cosign-release: 'v0.6.0'
+          cosign-release: 'v1.2.1'
       - name: Extract version of Go to use
         run: echo "GOVERSION=$(cat Dockerfile|grep golang | awk ' { print $2 } ' | sed -r 's/^.*://g'| uniq)" >> $GITHUB_ENV
       - uses: actions/setup-go@v2