Hi @Pratibha Dawar,
As per my knowledge and research, the only way to remove deleted contents form SharePoint is reindexing the site. Unfortunately, there is not a more permanent solution available currently. It is recommended to provide feedback to Microsoft via this portal: https://feedbackportal.microsoft.com/feedback/forum/06735c62-321c-ec11-b6e7-0022481f8472. Microsoft will take your idea into consideration if it is highly voted.
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