Unimply single_mechanical_arm from Nitori's backpack arm thing

BUR #22054 has been approved by @nonamethanks.

remove implication nobiiru_arm -> single_mechanical_arm

Why is this even an implication

Around 11 years ago someone had the tag implicate robotic_arms. Over 8 years ago robotic_arms was aliased to mechanical_arm. Around 3 years ago mechanical_arm was aliased to single_mechanical_arm.

The bulk update request #22054 (forum #263446) has been approved by @nonamethanks.

Do we have a tag for the kind of toy in post #713324? Because it doesn't look like the arm from touhou.