errors: decapitalize PBKDF2 error

Refs: nodejs#20816

Author: tniessen

lib/internal/errors.js

@@ -501,8 +501,7 @@ E('ERR_CRYPTO_HASH_FINALIZED', 'Digest already called', Error);
 E('ERR_CRYPTO_HASH_UPDATE_FAILED', 'Hash update failed', Error);
 E('ERR_CRYPTO_INVALID_DIGEST', 'Invalid digest: %s', TypeError);
 E('ERR_CRYPTO_INVALID_STATE', 'Invalid state for operation %s', Error);
-// TODO(bnoordhuis) Decapitalize: s/PBKDF2 Error/PBKDF2 error/
-E('ERR_CRYPTO_PBKDF2_ERROR', 'PBKDF2 Error', Error);
+E('ERR_CRYPTO_PBKDF2_ERROR', 'PBKDF2 error', Error);
 E('ERR_CRYPTO_SCRYPT_INVALID_PARAMETER', 'Invalid scrypt parameter', Error);
 E('ERR_CRYPTO_SCRYPT_NOT_SUPPORTED', 'Scrypt algorithm not supported', Error);
 // Switch to TypeError. The current implementation does not seem right.