If you want to remove "Category Archives:" and keep the Category's name on Wordpress site follow the steps below:

Install and activate RTFR.

The Real-Time Find and Replace plugin will be under TOOLS menu

1. Click "Add"

2. Replace (left box)
>Category Archives: <
with (right box)
3. Finally Click "Update Settings." The Category Archive will be gone from your WordPress site.

1922388 773230739431286 3696190187790159848 n?oh558b76975009efd4aeb10726c5afd8de&ampoe55536966 - Remove Category Archive in Wordpress

You might also want to replace (using the same technique):
Author Archives:
Tag Archives:
Daily Archives:
Monthly Archives:
Yearly Archives: