How do I convert a LED PIR Light to a switched only light
I looked online for a schematic diagram (a picture might help but probably not) and I didn't find any with 2 brown and 2 black wires.

You should see if you could possibly replace the PIR with a direct replacement.

If you proceed to hack the light you risk making it unusable. Of course in its current condition that would be the case. 

Without a schematic, my slightly educated guess would be, that if you cut the two brown wires and wire nut them together and then do the same with the black wires you will bypass the PIR. This is just a guess from the information you have posted. If it trips the breaker or the magical black smoke comes out of it, then you will know that was the wrong thing to do. Proceed at your own risk!

Good luck!