attr_encrypted does different things with `key` depending on what mode you are using:

1. In `:per_attribute_iv_and_salt` mode, it generates a hash with the salt:
https://github.com/attr-encrypted/encryptor/blob/c3a62c4a9e74686dd95e0548f9dc2a361fdc95d1/lib/encryptor.rb#L77.
There is no need to truncate the key to 32 bytes here.

2. In `:per_attribute_iv` mode, it sets the key directly to the password, so
truncation to 32 bytes is necessary.

Closes #47166