It's the one that was humble monthly last November. It's all episodes

Confirming with the GA creator is always the most reliable option, but SG itself already allows you to find the SteamDB page associated with a listing.

Right click on the image box [regardless of if it has an image or not] and select the copy link option to get the id of a listing.
Then, insert that link into google search and add " steamdb" at the end of your search text.
The first google search result should be the correct steamdb listing.

Go to https://help.steampowered.com/en/wizard/HelpWithGame or on Steam client Help in top left then Steam Support->Games, Software, etc.
Type hitman in search at bottom of page if its not in recent products at top
Click on Hitman (gold 47 icon)
CLick on I want to permanently remove this game from my account
Confirm
Resync your SG account with steam here https://www.steamgifts.com/account/settings/profile
and you should be good to go
P.S you can restore game whenever u like using same process you`ll see a new option at last stage that says restore instead of delete game