You could use
EXISTS and a correlated subquery to filter on rows whose
UserId has at least one audit event of id
UPDATE h SET IsActivated = 1 FROM [dbo].HRUser h WHERE EXISTS ( SELECT 1 FROM FROM dbo.[UserAudit] a WHERE a.UserId = h.UserId AND a.AuditTypeId = 14 )
Note that there is no point reopening the target table in the subquery; you just need to correlate it with the outer query.
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