chore: bump `@metamask/user-operation-controller` to `^21.0.0` #38319

Job	Run time
Determine whether this issue comment was on a pull request from a fork	8s
Prepare dependencies	1m 7s
React to the comment	6s
Update LavaMoat build policy	2m 12s
Update LavaMoat main application policy	5m 54s
Update LavaMoat beta application policy	6m 3s
Update LavaMoat flask application policy	5m 54s
Update LavaMoat mmi application policy	5m 48s
Commit the updated LavaMoat policies	19s
Check whether the policy update succeeded	1s
Comment about the policy update failure	8s
	27m 40s

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