Add AUR_BOT_SSH_PRIVATE_KEY env var for goreleaser

The AUR_BOT_SSH_PRIVATE_KEY environment variable needs to be set in
goreleaser so publishing the packages to AUR can work.

Signed-off-by: Aurel Canciu <aurelcanciu@gmail.com>

.github/workflows/release.yaml

@@ -85,3 +85,4 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           HOMEBREW_TAP_GITHUB_TOKEN: ${{ secrets.BOT_GITHUB_TOKEN }}
+          AUR_BOT_SSH_PRIVATE_KEY: ${{ secret.AUR_BOT_SSH_PRIVATE_KEY }}