In the first part of the text, Joseph Smith’s editing for the 1837 edition often involves clarification, such as here where he added the phrase “in my dream”. Nonetheless, the previous text has already made it very clear that everything Lehi saw was in his dream or vision:
Thus there is no overwhelming need to add “in my dream” two verses later.
Summary: Remove the unnecessary textual clarification “in my dream” from 1 Nephi 8:4.