docs: removed unnecessary brackets from belongs-to-many docs (#13373)
docs: removed unnecessary brackets from belongs-to-many docs (#13373)

Co-authored-by: Sascha Depold <df3f6e4cf69a28b4d0c05e64fe74fcb2d58ad376@users.noreply.github.com>
sequelize/sequelize,sequelize/sequelize,sequelize/sequelize