Remove imprecise clause from documenting comment
@@ -401,7 +401,7 @@ void mbedtls_cipher_free( mbedtls_cipher_context_t *ctx );
* the structure.
*
* \param ctx The context to initialize. This must be initialized.
- * \param cipher_info The cipher to use. This may not be \c NULL.
+ * \param cipher_info The cipher to use.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA on
