Remove redundant assertion in EncryptionOptions constructor

[kdomo]

The three-argument EncryptionOptions constructor asserts key twice:

Assert.hasText(algorithm, "Algorithm must not be empty");
Assert.notNull(key, "EncryptionKey must not be empty");
Assert.notNull(key, "QueryableEncryptionOptions must not be empty");

The third assertion re-checks key while its message names queryableEncryptionOptions. That parameter is @Nullable and the two-argument constructor passes null for it, so it must not be validated. The assertion is both redundant and misleading, so this removes it.

Closes #5241