Fix failing rustdoc GUI test

Author: GuillaumeGomez

tests/rustdoc-gui/search-result-color.goml

@@ -31,7 +31,7 @@ define-function: (
         // color of the typename (struct, module, method, ...) before search results
         assert-css: (
             ".result-name .typename",
-            {"color": "#888"},
+            {"color": |grey|},
             ALL,
         )
     },
@@ -75,6 +75,7 @@ store-value: (entry_color, "#0096cf") // color of the search entry
 store-value: (hover_entry_color, "#fff") // color of the hovered/focused search entry
 store-value: (background_color, "transparent") // background color
 store-value: (hover_background_color, "#3c3c3c") // hover background color
+store-value: (grey, "#999")
 
 call-function: (
     "check-result-color", (
@@ -186,6 +187,7 @@ store-value: (entry_color, "#ddd") // color of the search entry
 store-value: (hover_entry_color, "#ddd") // color of the hovered/focused search entry
 store-value: (background_color, "transparent") // background color
 store-value: (hover_background_color, "#616161") // hover background color
+store-value: (grey, "#ccc")
 
 call-function: (
     "check-result-color", (
@@ -282,6 +284,7 @@ store-value: (entry_color, "#000") // color of the search entry
 store-value: (hover_entry_color, "#000") // color of the hovered/focused search entry
 store-value: (background_color, "transparent") // background color
 store-value: (hover_background_color, "#ccc") // hover background color
+store-value: (grey, "#999")
 
 call-function: (
     "check-result-color", (