refactor(renderer): remove dead pinned-overlay scroll short-circuit

[phanen]

This never work since a and nil or b is always b

This seems a defensive programming introduced in a52636b

"only once scroll() on dialog first appear" have been implemented here:

opencode.nvim/lua/opencode/ui/renderer/events.lua

Line 156 in 3f1baf4

local should_scroll = ctx.render_state:get_part('permission-display-part') == nil

opencode.nvim/lua/opencode/ui/renderer/events.lua

Lines 176 to 178 in 3f1baf4

	if should_scroll then
	scroll(true)
	end