Revert "Add #to_s method to rails version on install Generator"

The Rails.version change was reverted in Rails.
This reverts commit e0b03fda8d19489b926bb7987c1f6f911d93fdc6.
Revert "Add #to_s method to rails version"

The Rails.version change was reverted in Rails.
This reverts commit 15b0e68677145906e791c140cff014f43c7bc45d.