Sorry but the IMDb has a policy not to remove correct and factual data.
Here is a reprint.
IMDb aims to be the most comprehensive and reliable source of information on movies, TV and celebrities. We are committed to accuracy and it is our longstanding policy not to alter or remove correct factual information from our records. If you notice an error or omission in our data, please submit a correction or deletion via the "Edit page" button located at the bottom of every name and title page and our staff will be happy to review it and make all applicable changes. We have a guide to adding data here.
However, IMDb will not remove accurate information. If you try to delete an item of data which is accurate, your delete will not be processed. Please be aware that attempts to delete accurate data will count against your overall accuracy rating and may result in all your submissions taking longer to process along with additional proof requirements.
You will need to be on the main IMDbPro desktop website rather than the app to do this.
You can also add a playing age range via the resume feature on IMDbPro -> https://help.imdb.com/article/imdbpro/manage-your-imdb-page/faqs-for-resume/GMLWQXHRJL84G66W