[PLT-6655] Remove 1024 character limit with text settings at system console, except sitename of custom branding (#6597)

* remove 1024 character limit with text settings at system console, except sitename of custom branding

* add ability to set textarea of TextSetting

webapp/utils/constants.jsx

@@ -931,7 +931,6 @@ export const Constants = {
     MAX_POSITION_LENGTH: 35,
     MIN_TRIGGER_LENGTH: 1,
     MAX_TRIGGER_LENGTH: 128,
-    MAX_TEXTSETTING_LENGTH: 1024,
     MAX_SITENAME_LENGTH: 30,
     TIME_SINCE_UPDATE_INTERVAL: 30000,
     MIN_HASHTAG_LINK_LENGTH: 3,