Hide frequently used Memojis from Emoji keyboard in iOS 13
From https://ioshacker.com/how-to/hide-memoji-stickers-ios-13-emoji-keyboard:


Swipe emoji keyboard towards the left and [hope that] iOS remembers the keyboard position. 


  iOS "remembers" the keyboard position for a few minutes only. When the app is unloaded and reloaded, the next time I open the emoji keyboard, there are the stupid memoji stickers again.


later:


  as of iOS 13.2, this behavior is no longer present, and the memoji drawer stays hidden now.

And, in the Messages app, bring up the keyboard in the app and tap on the grey A icon besides camera to bring up the feature bar. Swipe to find ● ● ● and then click Edit, and remove Memoji keyboard from the list of favorites  in the “more apps” list below. 


Update:


From the same site: Open Go to Keyboard Settings to remove the "Memoji Stickers". You can search for the same also in Settings itself. 


  disabling stickers via Settings only works in iOS 13.3. This option is not present in 13.2.