add missing type for macOS cert

Author: davegarthsimpson

.github/workflows/check-certificates.yml

@@ -74,6 +74,7 @@ jobs:
           - identifier: macOS signing certificate # Text used to identify certificate in notifications.
             certificate-secret: APPLE_SIGNING_CERTIFICATE_P12 # Name of the secret that contains the certificate.
             password-secret: KEYCHAIN_PASSWORD # Name of the secret that contains the certificate password.
+            type: pkcs12
           - identifier: Windows signing certificate
             certificate-secret: INSTALLER_CERT_WINDOWS_CER
             # The password for the Windows certificate is not needed, because its not a container, but a single certificate.