Remove Fluent Icons mistakenly added to MDL2 folder

These 30 icon images were accidentally added to the segoe-mdl-2 folder
instead of the segoe-fluent-icons folder. They are not referenced in
the segoe-ui-symbol-font.md documentation and should be removed.

The correct versions are already in hub/apps/design/style/images/glyphs/segoe-fluent-icons/

Co-authored-by: Copilot <[email protected]>

Author: GrantMeStrength