PocketBook: Simplify openLink impl - use inkview.OpenBook instead

Somewhat unintuitively, OpenBook does exactly what we want if we pass
the browser binary as the book and the URL as parameters.

It does a couple extra things we don't need, like checking if the
browser binary is being viewed by the built-in epub reading software,
and possibly some more stuff I don't quite understand, but at the end it
does almost exactly what OpenTask from the new PocketBook SDK does.

Actually, OpenBook2 is closer to OpenTask, as it takes `const char **argv`
rather than a single argument, but: we don't need multiple arguments,
and the single-argument version might work better on older PocketBook
firmwares (like the PB624 which is stuck with InkView 4.4).

frontend/device/pocketbook/device.lua

@@ -442,40 +442,9 @@ function PocketBook:canOpenLink()
 end
 
 function PocketBook:openLink(link)
-    if not link or type(link) ~= "string" then return end
-
-    -- SendRequestToNoWait only available in PocketBook SDK since 5.17
-    local inkview_SendRequestTo
-    if pcall(function() local _ = inkview.SendRequestToNoWait end) then
-        inkview_SendRequestTo = function(t, r, d, l) inkview.SendRequestToNoWait(t, r, d, l, 0) end
-    else
-        inkview_SendRequestTo = function(t, r, d, l) inkview.SendRequestTo(t, r, d, l, 0, 2000) end
-    end
-
-    local appname = "browser.app"
-    local task = inkview.FindTaskByAppName(appname)
-    if task > 0 then
-        local data = ffi.new("void *[1]")
-        local len = ffi.new("int[1]")
-        inkview.PackParameters(1, ffi.new("const char *[1]", {link}), data, len)
-        inkview_SendRequestTo(task, C.REQ_OPENBOOK2, data[0], len[0])
-        C.free(data[0])
-        inkview.SetActiveTask(task, 0)
-    else
-        local _, bin = getBrowser()
-        local args = ffi.new("const char *[3]", {bin, link, nil})
-        inkview.NewTask(bin, ffi.cast("char **", args), appname, appname, nil, C.TASK_MAKEACTIVE)
-    end
-    -- the above logic is available in newer PocketBook SDKs [1] as OpenTask:
-    --
-    --     ffi.cdef[[ int OpenTask(const char *, int, const char **, int); ]]
-    --
-    --     local argv = ffi.new("const char *[1]", {link})
-    --     inkview.OpenTask("/usr/bin/browser.app", 1, argv, C.TASK_MAKEACTIVE)
-    --
-    -- we're using an older SDK for compatibility, so we need to handle this manually
-    --
-    -- [1]: https://github.com/pocketbook/SDK_6.3.0/blob/6.5/SDK-B288/usr/arm-obreey-linux-gnueabi/sysroot/usr/local/include/inkview.h
+    local found, bin = getBrowser()
+    if not found or not link or type(link) ~= "string" then return end
+    inkview.OpenBook(bin, link, 0)
 end
 
 -- Pocketbook HW rotation modes start from landsape, CCW