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

Co-authored-by: Sascha Depold <sdepold@users.noreply.github.com>

lib/associations/belongs-to-many.js

@@ -48,7 +48,6 @@ const Op = require('../operators');
  * const projects = await user.getProjects();
  * const projects = await user.getProjects();
  * const p1 = projects[0];
  * const p1 = projects[0];
  * p1.UserProjects.started // Is this project started yet?
  * p1.UserProjects.started // Is this project started yet?
- * })
  * ```
  * ```
  *
  *
  * In the API reference below, add the name of the association to the method, e.g. for `User.belongsToMany(Project)` the getter will be `user.getProjects()`.
  * In the API reference below, add the name of the association to the method, e.g. for `User.belongsToMany(Project)` the getter will be `user.getProjects()`.