I go up short hills like that and there are ways and means of getting up without having to dismount. I like to practice for when i do dirt & often just sit in the saddle on the roadie when I encounter some sort of hill.

Why not shift your weight around in smidgen bits? When you're going up the steepest part of the hill do as mountain bikers do "boobs to de tube" and keep moving.

Engage your core muscles & don't hold onto your handlebars for dear life. Don't worry about how slow you go as the hill will end soon enough.