[ui] Fix light-theme blue gradient (#21336)

## Summary & Motivation

Fix a CSS syntax error on the light-theme blue gradient.

## How I Tested These Changes

View new catalog page in light theme, verify that the gradient renders correctly.

js_modules/dagster-ui/packages/ui-components/src/theme/lightThemeColors.tsx

@@ -120,6 +120,6 @@ export const lightThemeColors = css`
   --color-data-viz-yellow-alt: var(--color-dataviz-yellow300);
   --color-blue-gradient: linear-gradient(
     var(--color-core-gray10),
-    var(--color-translucent-blue10) ; 100%
+    var(--color-translucent-blue10) 100%
   );
 `;