Yes, it is possible and OK to upgrade piaware only while running dump1090-mutability.
However you will loose the benefit of Adaptive Gain which is not available in dump1090-mutabilty.
As your OS is an old one (Stretch), I recommend to write on a spare microSD card latest PiAware SD Card image which is Raspian Buster based. It will have everything latest version. You can slip out old microSD card, slip in the freshly written spare microSD card, and you are upgraded.
Guide:
(1) https://flightaware.com/adsb/piaware/build/
(2) How to Install and Configure Piaware 5.0 SD card image - Quickstart Guide Note:do not use image in this guide, it is old version 5.0