What is the meaning of pct_trend_adjusted in FiveThirtyEight's polling data?
Looking at the methodology provided by FiveThirtyEight, it seems as though this figure (i.e. polling figures on state level) is adjusted for trends in national polls. See differentiator 1 on the linked page for more info:

Basically, in states that haven’t been polled recently, we make
inferences about what’s going on there using national polls or polls
from other states that have been surveyed recently