Remove token column from ci_builds table

What does this MR do and why?

Related to #339192 (closed)

The column was ignored in %15.2 by !91047 (merged)

Screenshots or screen recordings

> bin/rails db:migrate
main: == 20220720123249 RemoveTokenColumnFromCiBuilds: migrating ====================
main: -- remove_column(:ci_builds, :token, :string)
main:    -> 0.0022s
main: == 20220720123249 RemoveTokenColumnFromCiBuilds: migrated (0.0030s) ===========

ci: == 20220720123249 RemoveTokenColumnFromCiBuilds: migrating ====================
ci: -- remove_column(:ci_builds, :token, :string)
ci:    -> 0.0013s
ci: == 20220720123249 RemoveTokenColumnFromCiBuilds: migrated (0.0015s) ===========

> bin/rails db:rollback:main
main: == 20220720123249 RemoveTokenColumnFromCiBuilds: reverting ====================
main: -- add_column(:ci_builds, :token, :string)
main:    -> 0.0034s
main: == 20220720123249 RemoveTokenColumnFromCiBuilds: reverted (0.0058s) ===========

> bin/rails db:rollback:ci
ci: == 20220720123249 RemoveTokenColumnFromCiBuilds: reverting ====================
ci: -- add_column(:ci_builds, :token, :string)
ci:    -> 0.0023s
ci: == 20220720123249 RemoveTokenColumnFromCiBuilds: reverted (0.0050s) ===========

Impact

Reduced ci_builds size by 2.2GB

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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