Revert "docs: Add setSessionId to reference website (#397)"

This reverts commit c47c6f4.

Author: kelvin-lu

src/amplitude-client.js

@@ -974,14 +974,6 @@ AmplitudeClient.prototype.setOptOut = function setOptOut(enable) {
   }
 };
 
-/**
- * Set a custom Session ID for the current session.
- * Note: This is not recommended unless you know what you are doing because the Session ID of a session is utilized for all session metrics in Amplitude.
- * The Session ID to set for the current session must be in milliseconds since epoch (Unix Timestamp).
- * @public
- * @param {int} sessionId to set.
- * @example amplitudeClient.setSessionId(1622158968000);
- */
 AmplitudeClient.prototype.setSessionId = function setSessionId(sessionId) {
   if (!utils.validateInput(sessionId, 'sessionId', 'number')) {
     return;