Return a list of IR blocks with all Backtrack blocks removed.

def remove_backtrack_blocks_from_fold(folded_ir_blocks):
    """Return a list of IR blocks with all Backtrack blocks removed."""
    new_folded_ir_blocks = []
    for block in folded_ir_blocks:
        if not isinstance(block, Backtrack):
            new_folded_ir_blocks.append(block)
    return new_folded_ir_blocks