Remove old breadcrumb-item-text class to fix truncation on mobile

What does this MR do and why?

Removes the old breadcrumb-item-text class to fix breadcrumb title truncation on mobile.

This was conflicting with the newer classes from GlBreadcrumb styles.

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Go to a project that has an avatar. (The bug only happened when the project/group/user had an avatar ... CSS 🙄)
• Go to any page where breadcrumbs overflow on a mobile view width, like the "New issue".
• Give the avatar breadcrumb a long title (either via devtools or for real in project settings)
• Shrink your window to around 500px and you should be able to reproduce the bug on master / verify the fix here.