Remove foreign key ci_daily_build_group_report_results.group_id

What does this MR do and why?

The loose foreign key was already added for this in !77721 (merged) . We've confirmed in #348269 (closed) that it is indeed safe to swap these foreign keys for loose foreign keys.

Migrations

Up

== 20220106231518 RemoveForeignKeyCiDailyBuildGroupReportResultsGroupId: migrating
-- transaction_open?()
   -> 0.0000s
-- foreign_keys(:ci_daily_build_group_report_results)
   -> 0.0031s
-- remove_foreign_key(:ci_daily_build_group_report_results, :namespaces, {:name=>"fk_fd1858fefd"})
   -> 0.0039s
== 20220106231518 RemoveForeignKeyCiDailyBuildGroupReportResultsGroupId: migrated (0.0169s)

Down

== 20220106231518 RemoveForeignKeyCiDailyBuildGroupReportResultsGroupId: reverting
-- transaction_open?()
   -> 0.0000s
-- foreign_keys(:ci_daily_build_group_report_results)
   -> 0.0031s
-- transaction_open?()
   -> 0.0000s
-- execute("ALTER TABLE ci_daily_build_group_report_results\nADD CONSTRAINT fk_fd1858fefd\nFOREIGN KEY (group_id)\nREFERENCES namespaces (id)\nON DELETE CASCADE\nNOT VALID;\n")
   -> 0.0028s
-- execute("ALTER TABLE ci_daily_build_group_report_results VALIDATE CONSTRAINT fk_fd1858fefd;")
   -> 0.0027s
== 20220106231518 RemoveForeignKeyCiDailyBuildGroupReportResultsGroupId: reverted (0.0162s)

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Related to #348269 (closed)