Tag alias/implication: pixiv_mahou_gakuen_2.0 -> pixiv_mahou_gakuen

create implication pixiv_mahou_gakuen_2.0 -> pixiv_mahou_gakuen

Link to implication

We currently just have Pixiv Mahou Gakuen (Pixiv魔砲学園) but apparently Pixiv Mahou Gakuen 2.0 (Pixiv魔砲学園2.0) is also a thing.

Feel free to alias instead; I don't know what the difference between the two is supposed to be.

Nobody really uses mahou_gakuen so an alias is probably fine.

Done as alias