Reset job_token_scope_enabled setting to false

What does this MR do?

Related to #333002 (closed)

This MR is based on top of !64962 (merged) where we remove the default: true value at the model-level for this setting. Given that the feature flag hasn't been fully enabled for this feature we need to start with the setting to be false for all projects.

In a follow-up MR, after we enabled the feature flag by default we will also change the default value to true so that it will apply to all new projects.

Database migration

rails db:migrate:redo VERSION=20210628124505

== 20210628124505 ResetJobTokenScopeEnabled: reverting ========================
== 20210628124505 ResetJobTokenScopeEnabled: reverted (0.0000s) ===============

== 20210628124505 ResetJobTokenScopeEnabled: migrating ========================
-- remove_column(:project_ci_cd_settings, :job_token_scope_enabled)
   -> 0.0027s
-- add_column(:project_ci_cd_settings, :job_token_scope_enabled, :boolean, {:default=>false, :null=>false})
   -> 0.0044s
== 20210628124505 ResetJobTokenScopeEnabled: migrated (0.0200s) ===============

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Does this MR meet the acceptance criteria?

Conformity

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• This change is backwards compatible across updates, or this does not apply.

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• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
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Security

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