doc: add missing description of argument in subtle.encrypt

Description of third argument(data) in subtle.encrypt is missed,
so add it.

PR-URL: #50578
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

doc/api/webcrypto.md

@@ -684,6 +684,7 @@ added: v15.0.0
 
 * `algorithm`: {RsaOaepParams|AesCtrParams|AesCbcParams|AesGcmParams}
 * `key`: {CryptoKey}
+* `data`: {ArrayBuffer|TypedArray|DataView|Buffer}
 * Returns: {Promise} containing {ArrayBuffer}
 
 Using the method and parameters specified by `algorithm` and the keying