Revert "exo: temporarily clamp display scale factor to 2"

This reverts commit a96ef56c.

Reason for revert: Parallels have upgraded to QT 5.15 hence the workaround is no longer needed.

Original change's description:
> exo: temporarily clamp display scale factor to 2
>
> Version of QT currently in use by Parallels Desktop does not render
> correctly when display scale factor is above 2, so let's use 2 as the
> upper bound until they switch to a newer version of QT (5.15 should
> have the fix).
>
> Bug: b/169984627
> Change-Id: Idd31b9a737833fa48ab6b20ae8da5f1bf951b3ff
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2446720
> Commit-Queue: Dmitry Torokhov <dtor@chromium.org>
> Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#816020}

TBR=oshima@chromium.org,dtor@chromium.org,edcourtney@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: b/169984627
Bug: 1137268
Change-Id: Iba38d0df84c87ed7ade2986704f9d29d5ec75f78
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2570309Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Dmitry Torokhov <dtor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833102}

components/exo/wayland/wayland_display_observer.cc

@@ -117,11 +117,8 @@ bool WaylandDisplayHandler::SendDisplayMetrics(const display::Display& display,
       WL_OUTPUT_SCALE_SINCE_VERSION) {
     // wl_output only supports integer scaling, so if device scale factor is
     // fractional we need to round it up to the closest integer.
-    // TODO(b/169984627, crbug:1137268): remove clamping to 2 once Parallels
-    // switches to a newer version of QT.
-    wl_output_send_scale(
-        output_resource_,
-        std::min(std::ceil(display.device_scale_factor()), 2.0f));
+    wl_output_send_scale(output_resource_,
+                         std::ceil(display.device_scale_factor()));
   }
 
   // TODO(reveman): Send real list of modes.