Fixed Mystic Lava staff not counting as earth runes

What has been done in this MR?

Added Mystic Lava Staff to list of staves that provide Earth runes Issue: #1895

What should testers check?

Check spells that require earth runes. Has been checked against bolt enchant and Earth Wave

• I have tested these changes thoroughly.

• I used the relevant Zaros tool for any JSON edits where possible, and have attached screenshots of any changes.