ci: Fix broken key importing (#474)

gpg apparently uses tty for printing warnings
(in this case about trust level for the new key)

Because there's no valid tty in GitHub Actions (or any other CI)
we reflect that by passing extra flags to gpg.

.github/workflows/release.yml

@@ -62,7 +62,7 @@ jobs:
           hc-releases version
       -
         name: Import key for archive signing
-        run: echo -e "${{ secrets.GPG_PRIVATE_KEY }}" | gpg --import
+        run: echo -e "${{ secrets.GPG_PRIVATE_KEY }}" | gpg --import --batch --no-tty
       - 
         name: Configure AWS Credentials
         uses: aws-actions/configure-aws-credentials@v1