Fix some visual bugs w/ edit predictions (#24591)

* correct the size of key binding icons
* avoid spurious modifier in 'jump to edit' popover when already
previewing
* fix height of the edit preview popover

Release Notes:

- N/A

Co-authored-by: agu-z <hi@aguz.me>

crates/ui/src/components/icon.rs

@@ -66,7 +66,7 @@ pub enum IconSize {
     Medium,
     /// 48px
     XLarge,
-    Custom(Pixels),
+    Custom(Rems),
 }
 
 impl IconSize {
@@ -77,7 +77,7 @@ impl IconSize {
             IconSize::Small => rems_from_px(14.),
             IconSize::Medium => rems_from_px(16.),
             IconSize::XLarge => rems_from_px(48.),
-            IconSize::Custom(size) => rems_from_px(size.into()),
+            IconSize::Custom(size) => size,
         }
     }
 
@@ -95,7 +95,7 @@ impl IconSize {
             IconSize::Medium => DynamicSpacing::Base02.px(cx),
             IconSize::XLarge => DynamicSpacing::Base02.px(cx),
             // TODO: Wire into dynamic spacing
-            IconSize::Custom(size) => px(size.into()),
+            IconSize::Custom(size) => size.to_pixels(window.rem_size()),
         };
 
         (icon_size, padding)