Here ya go:

9.1.3.D.9.e, "The driver’s seat (only) shall be replaced with a one-piece bucket-type race seat. Factory seat tracks/brackets may be modified, reinforced, and/or removed to facilitate replacement mountings provided they perform no other function. All other seats may be removed."

My emphasis.

I expect entertaining arguments that these items in question aren't "brackets"; well, they are. Anything used to attach and/or support the seat to the car is a "seat bracket"; those sheet metal humps on the floor serve no purpose other than to support/mount the seat. Thus, they are brackets and are legal to remove.

GA