The mold in your shower is the non toxic kind but even non toxic mold can still make a person or people sick so it should always be removed anyway.
Although the mold in your shower is likely not the toxic kind of mold that can cause serious problems it still is not good to have the mold in your shower as the mold in your shower can cause rashes, headaches, dizziness, nausea, allergies, asthma attacks, and in some cases serious lung infections especially if you have other lung conditions.