I've had that happen to me before in different types of soil. That usually happens if the soil is either not (mostly) sterile (minus potential beneficials added) and/or has been left outside and has been seeded by grasses or other things. It can happen if you have real manure and compost in your soil. One of the best soils I've ever used in general for gardening tends to always have a few sprouts come up.
I have learned as well that leaving some soil mixes (such as super soil mixes) sit outside for a year helps it "cook" just a little bit more and gives it that "edge" for growing but also can sprout some other seed that may be in there.
You could always sterilize your soil if you really wanted to... I guess... However, i don't know if you're going to want to as there's usually beneficials in most soil mixes so sterilizing the bag a second time won't usually help.
I have never found it to be any type of issue and the seeds usually take off fine, just watch a little closer your plants over the grow for any potential mould, algae, and more over, gnats. I night suggest after the seed is a bit older, being religious about gnats and getting on top of them if you see one because they are just annoying.
If you want to remove the non-cannabis seedlings; You can wait till your seedling comes up and pluck the other sprouts out if you are so inclined (and so it doesn't take extra root space/nutrients from your plant). I personally pluck them once the seed is up but keep them for a few days because it it gives me a warm fuzzy feeling.