Remove is_active column from grafana's user view

[lucyb]

This column has been removed from Job Server's user table, so it needs to be removed from the corresponding view as well.

I've recreated the view in the database already by running the following in the production database:

CREATE VIEW jobserver_user_grafana AS SELECT id,last_login,username,date_joined,fullname,created_by_id,login_token_expires_at,pat_expires_at,roles FROM jobserver_user;

GRANT SELECT ON jobserver_user_grafana TO grafanareader;