Fix railties dependency issue for rails version >= 6.0
Remove railties dependency's max version to support gem on Rails >= 6.0
Facing issue while using this gem on Rails >= 6.0
gentelella-rails was resolved to 0.1.11, which depends on
switchery-rails was resolved to 0.8.1.1, which depends on
railties (>= 3.2, < 6.0)