The pgx_set_keystore_passphrase function changes the file-based keystore passphrase.
Specify the current passphrase in oldPassphrase, and a new passphrase in newPassphrase.
The passphrase is a string of 8 to 200 bytes.
Only superusers can execute this function. Also, this function cannot be executed within a transaction block. Processing is not affected by whether the keystore is open.