fix(ui): prevent Avatar from shrinking in flex layouts

Signed-off-by: Johan Persson <johanopersson@gmail.com>

.changeset/fix-avatar-flex-shrink.md

@@ -0,0 +1,7 @@
+---
+'@backstage/ui': patch
+---
+
+Fixed `Avatar` becoming elliptical in flex layouts by preventing it from shrinking.
+
+**Affected components:** Avatar

packages/ui/src/components/Avatar/Avatar.module.css

@@ -30,6 +30,7 @@
     font-size: 1rem;
     line-height: 1;
     overflow: hidden;
+    flex-shrink: 0;
     height: 2rem;
     width: 2rem;
   }