Can I Change or Delete the List of Entries That Appears When I Edit a Text Field in Salesforce Classic?
No. These auto-complete entries that appear when you are editing certain text fields are a feature of Internet Explorer.
The browser remembers text that you entered previously and provides a list of those entries for you to automatically complete the field. If you would like to turn off this feature, click Tools on your browser’s menu bar. Select Internet Options, click the Content tab, and then choose the AutoComplete button to change your browser’s settings.