The Bible has tons of edits like this, it’s fun to spot them—and even more so to guess the intent behind them. Often when a seemingly irrelevant detail (or an entire chapter) is inserted in the middle of a story, that’s an edit (although there are also genuine errors). In general, the Bible is not as well put-together as people tend to think. In this case, whoever wrote this wanted to make clear that Judaism does not condone human sacrifice, in contrast to other contemporary religions.
Others (chiefly those who consider the text to be holy) interpret the pronoun change as indicative of an emotional separation between Abraham and his son, as if following these events they don’t want to walk together any more.
As a fun fact, some interpretations say that by binding Isaac and being ready to proceed, Abraham failed the test, either in the eyes of God or at the very least in the eyes of the author. The second verse has God saying (JPS Contemporary Torah)
And after stopping him, the angel (which is identified with God) says
The description of Abraham’s love for Isaac is missing, despite identical phrasing (also in Hebrew) otherwise. It’s as if God (or the author) is taunting Abraham.
This also raises a concern about God’s omniscience; he says “now I know that you fear God”, as if he wasn’t previously sure. There are many ways to resolve this, but the Bible is just very inconsistent everywhere.