Add migration to confirm bot

What does this MR do?

This MR addressed one task from #292927 (closed)

add migration for make bot confirmed !49167 (comment 464281322) this should be addressed before feature flag is turned off

Details

We have Security Bot that is used for the auto-fix feature, which is right now under a feature flag. The bot was initially created without confirmed_at field so it should be changed with migration.

Migration

up

== 20201222170801 UpdateSecurityBot: migrating ================================
== 20201222170801 UpdateSecurityBot: migrated (0.0800s) =======================

down

== 20201222170801 UpdateSecurityBot: reverting ================================
== 20201222170801 UpdateSecurityBot: reverted (0.0000s) =======================

Screenshots (strongly suggested)

not applicable

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Related to #292927 (closed)