First of all Fragment of Mogo

It is very weird in a sense and also hard for me to see the purpose of this change, since there already was an HP / Power Armor item in 'Entropy Aegis', however lets say it's a legit change (which i don't think it is) I see that you are trying to involve 'Claw of Horus' as the new HP / Attack armor item, maybe to see it used more or to get it involved in the current meta, however the exclusion of 'Claw of Horus' from regular builds in competitive play has been a series of steps.

To explain the 'Claw Of Horus' exclusion from builds one needs to take note of step by step changes.

State 1. Claw of Horus had lifesteal, which was then removed, at the same close time to when Nightmare Batman was 'over-nerfed' and therefore people started trying different stuff on other champions, and where 'Claw of Horus' gave a somewhat option, there was numerous better ones.

State 2. Fragment of Mogo is changed into a PA/HP item and Claw of Horus transitions into a AA/HP item, one would think oh great change this could be awesome, except one could buy a suit of sorrows, and a Crime Bible, sure it would take 2 slots, but that gives a huge difference in stats and for not much more in price. Claw costs 3k Credits whilst Crime Bible is only 1k and Suit is 3k just like the Claw.
Down to a direct choice however, one easily notes that the numbers on Claw of horus as it is makes the item completely not worth investing in. 3k for 20 Attack Armor and 200Hp? It is a joke in comparison to 100 Attack armor with 30% attack reflect for 3k Credits and 475 HP at full stacks for an added 1.25k Credits.

As a positive comment, I have yet to test this in action however Claw of Horus, 'MIGHT' somewhat be applicable onto Supergirl, however i think it will not be enough to boost her lack of potential in the late-mid game. Currently supergirl excels in the early-mid game where if one rushes a good stack of damage, can be a high threat to the enemy carries or untanked targets, where Late-Game can be a threat to everyone if built correctly but results in being too easily blown up by enemy carries if controlled correctly.

Secondly the change to Booster Gold's Power Suit.

Due to the high amount of choices in Attack Armor items, as well as cooldown reduction items, this was already not a high priority choice item, but as a whole, in my personal opinion, the nerf was simply not necessary.

Booster Gold's Power Suit is seeing a slight decrease to its stats: its Tier 3 Cooldown Reduction is lowered to 10% (was 15%).

Also to add, the 'Slight' change that was mentioned, in a simple grade 3 mathematical point of view is 1/3 of its total stat at tier 3, which definatley shouldn't be regarded as 'Slight'.

In a competitive perspective, I don't think this item will be seen at all in competitive play as these stats are right now. As an item, one will buy it with champions who make use of shields and skill casting, where cooldown reduction is necessary and example is Atomic Wonder Woman or, Wonder Woman Prime, now, in wonder woman prime's case, she needs to be VERY tanky in order to not die when ulting multiple targets, since shes a champion that wants to be in the middle of the fight, and when one compares 50 armor to the suit of sorrows which gives 100 at the same price, with the added reflect that synergises well with her kit, as an armor stat option, booster gold is alread not 1st choice. Also at the same price, one could get Metallo's Heart. which gives 70 attack armor (20 more) and also 10% cooldown recution.