[Bug]: Stop icon is validating design guidelines

**Describe the bug**

The stop icon is using round corners, which is a design crime according to guidelines:

**To Reproduce**

Steps to reproduce the behavior:

1. View [vanilla icons](https://vanillaframework.io/docs/patterns/icons)
2. search for the stop icon

**Expected behavior**

Corners should be sharp.

**Screenshots**

**Additional context**

This was initially discovered by @mattea-turic