build-ca: Command 'req', remove SSL option '-keyout'

[TinCanTech]

OpenSSL command 'req', option '-keyout' behaves differently between OpenSSL v3.x verses v1.x

When the private key is encrypted:

• v1.x ignores '-keyout' and does not create a new key.
• v3.x creates a new key with different parameters to the original key.

v3.x creates the original key, encrypted by AES-256-CBC; then creates the unnecessary, secondary key, encrypted by DES-EDE3-CBC.

Because EasyRSA has already generated the private key, the 'req' command must not generate a secondary key.