[4.0.0-alpha.19] [Request] Print Pregnancy control agents message only once

If you have a rule setting pregnancy control agents, the "X is pregnant, so she has been put on the rapid/slowing gestation agents" message always shows up, even if she was taking them already. It should be shown only once.

assigned to @Arkerthan

mentioned in merge request !11099 (merged)

closed with merge request !11099 (merged)

mentioned in commit 955f0e76

mentioned in issue #4441