tls: Stop hardcoding 2048 bit RSA key length

These are rejected as "too weak" by the "FUTURE" crypto policy. Let the
tools decide about appropriate defaults rather.

Thanks to Renaud Métrich for finding this!

https://issues.redhat.com/browse/RHEL-78645

src/tls/cockpit-certificate-helper.in

@@ -30,7 +30,6 @@ install_key() {
 selfsign_sscg() {
     sscg --quiet \
         --lifetime "${DAYS}" \
-        --key-strength 2048 \
         --cert-key-file "${KEYFILE}" \
         --cert-file "${CERTFILE}" \
         --ca-file "${CA_FILE}" \
@@ -43,7 +42,7 @@ selfsign_sscg() {
 selfsign_openssl() {
     openssl req -x509 \
         -days "${DAYS}" \
-        -newkey rsa:2048 \
+        -newkey rsa \
         -keyout "${KEYFILE}" \
         -keyform PEM \
         -nodes \