Can not override template for specific view
You either haven't rebuilt cache, or the page you're viewing isn't being generated by your Categories Views. It seems to be generated by the default Taxonomy term Views. Or you're viewing the wrong page :) 

Views templates debug info is shown further down the source HTML, you won't find it at the top of the source page. Try looking below the main page heading in the source HTML, that's there the page views will start with their own templates. 

This issue is also relevant:
Views file name suggestions often missing from Twig debugging

Especially the fifth comment there:
#5

Also:
[PP-3] Twig debug output does not display all suggestions when an array of theme hooks is passed to #theme

I haven't tried this module but it may be relevant:
Views Templates