Scripts/Quests: Fix Red Snapper - Very Tasty! GOb

Fix 'School of Red Snapper' now disappear correctly when using 'Draenei Fishing Net', the bug is caused because the GameObject is SpellFocus type.

Fix #1673
Closes #13748

(cherry picked from commit b0b7a55bdba20aad5b7914c55933daa70afe59ba)