Use correct background color for "show other declarations button" (#818) rdar://126922233 (#821)

Use correct background color for "show other declarations button" (#818)  rdar://126922233

Author: hqhhuang

src/components/DocumentationTopic.vue

@@ -740,7 +740,8 @@ $space-size: 15px;
     top: 50%;
     left: 50%;
     transform: translate(-50%, -50%);
-    background-color: var(--color-fill); // cover border line
+    // cover border line
+    background-color: var(--color-other-decl-button);
     padding: 5px 15px;
     color: var(--colors-link, var(--color-link));
     z-index: 1;

src/styles/core/colors/_light.scss

@@ -134,6 +134,7 @@
   --color-nav-dark-uiblur-expanded: #{change-color(dark-color(fill-tertiary), $alpha: 0.9)};
   --color-nav-dark-uiblur-stuck: #{change-color(dark-color(fill-tertiary), $alpha: 0.7)};
   --color-nav-dark-root-subhead: #{dark-color(tutorials-teal)};
+  --color-other-decl-button: var(--color-text-background);
   --color-runtime-preview-background: var(--color-fill-tertiary);
   --color-runtime-preview-disabled-text: #{change-color(light-color(figure-gray-secondary), $alpha: 0.6)};
   --color-runtime-preview-text: var(--color-figure-gray-secondary);