Fix a conditional import reftest.

This test fails on windows due to fuzzy pixels where the F starts. It
also fails on Edge according to wpt.fyi.

Add some padding so that the F doesn't bleed out of the container with
Windows' default font.

Differential Revision: https://phabricator.services.mozilla.com/D175515

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1828188
gecko-commit: cce2ee8b24dddbaa0f92ceedec7743a8859d7add
gecko-reviewers: CanadaHonk
diff --git a/css/css-cascade/import-conditional-001.html b/css/css-cascade/import-conditional-001.html
index 9bdbbcb..a841f26 100644
--- a/css/css-cascade/import-conditional-001.html
+++ b/css/css-cascade/import-conditional-001.html
@@ -16,8 +16,10 @@
   @import "support/test-red.css"
     (max-width: 1px), nonsense;
   div {
+    box-sizing: border-box;
     width: 100px;
     height: 100px;
+    padding: 5px; /* Avoids text antialiasing issues */
     background: red;
   }
   </style>