Files app: Fix QuickView dialog width and height

The issue was introduced by CL:2258897.

Similar fix has been applied to <cr-dialog> CL:2538530.

QuickView seems to be the only use of <dialog> in our code base, Code
Search query: "<dialog file:^ui/file_manager/".

Test: Checked visually running linux-chromeos locally.
Change-Id: I87f5b0a230dc738159d4fb6d47508a2f3ed30669
Fixed: 1152913
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2560701
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831200}

ui/file_manager/file_manager/foreground/elements/files_quick_view.css

@@ -13,6 +13,8 @@ dialog {
   font-size: 100%;
   height: 100%;
   margin: 0;
+  max-height: initial;
+  max-width: initial;
   opacity: 0;
   padding: 0;
   width: 100%;