core/input.css: remove anchor fallback position, always anchor bottom left

input.css

···
 }
 
 .site-navigation-dropdown-trigger {
-        anchor-name: --dropdown-trigger;
-    }
+    anchor-name: --dropdown-trigger;
+}
 
 .site-navigation-popover {
-    position: absolute;
     margin: 0;
     inset: auto;
     position-anchor: --dropdown-trigger;
-    position-area: bottom right;
-    position-try-fallbacks: --bottom-left;
-}
-
-@position-try --bottom-left {
     position-area: bottom left;
-}
+}