Hey There!,
Deleting a page of a site is always tricky, so I would always consider looking at other factors that may be causing this page to still show in Google results.
Firstly I would check the sitemap. The sitemap is an easy way to tell Google what pages you want indexed. I would remove the page in question from the sitemap if you haven't already, then I would log into Google Search Console and upload the new one. This should provide Google with a fresh new sitemap without the 404 Page hopefully preventing the page being indexed.
Another consideration when removing a page from the site, is to ensure there are no other sites still linking to that page, if Google can access your site from another page or another site, chances are it will index it.
For this I would implement a 301 re-direct to redirect users(and bots) visiting that page to a relevant equivalent.
Hope this helps!
Thanks,
Ian