use white instead of white-static

Author: mukunku

packages/stacks-classic/lib/components/avatar/avatar.less

@@ -1,6 +1,6 @@
 .s-avatar {
     --_av-size: var(--su16);
-    --_av-bg: var(--_white-static); // Force a white background color for when we have transparent avatars
+    --_av-bg: var(--white); // Use a solid background color to prevent transparent avatars from blending with the background
     --_av-fs-letter: calc(var(--su12) - var(--su1));
     --_av-scale-badge: 1;