fix color-gradient

packages/app/src/styles/theme/_apply-colors-light.scss

@@ -93,10 +93,10 @@
   */
   .nologin {
     // background color
-    --color-gradient: #3e4d6c;
-    background: linear-gradient(45deg, hsl.darken(var(--color-gradient), 30%) 0%, hsla(340, 100%, 55%, 0) 70%),
+    $color-gradient: #3c465c;
+    background: linear-gradient(45deg, darken($color-gradient, 30%) 0%, hsla(340, 100%, 55%, 0) 70%),
       linear-gradient(135deg, var.$growi-green 10%, hsla(225, 95%, 50%, 0) 70%), linear-gradient(225deg, var.$growi-blue 10%, hsla(140, 90%, 50%, 0) 80%),
-      linear-gradient(315deg, hsl.darken(var(--color-gradient), 25%) 100%, hsla(35, 95%, 55%, 0) 70%);
+      linear-gradient(315deg, darken($color-gradient, 25%) 100%, hsla(35, 95%, 55%, 0) 70%);
 
     .nologin-header {
       background-color: rgba(white, 0.5);