doc(core): Fix outdated JSDoc in beforeSendSpan (getsentry#17815)

Spotted that we still documented that the root span does not go through
`beforeSendSpan`. This is outdated. Since v9, we also pass the root span
to the callback.

packages/core/src/types-hoist/options.ts

@@ -408,9 +408,6 @@ export interface ClientOptions<TO extends BaseTransportOptions = BaseTransportOp
   /**
    * This function can be defined to modify a child span before it's sent.
    *
-   * Note that this function is only called for child spans and not for the root span (formerly known as transaction).
-   * If you want to modify or drop the root span, use {@link CoreOptions.beforeSendTransaction} instead.
-   *
    * @param span The span generated by the SDK.
    *
    * @returns The modified span payload that will be sent.