Migrate GUI colors test to original CSS color format

Author: GuillaumeGomez

Diff for: tests/rustdoc-gui/anchors.goml

@@ -75,35 +75,35 @@ call-function: (
     "check-colors",
     {
         "theme": "ayu",
-        "main_color": "rgb(197, 197, 197)",
-        "title_color": "rgb(255, 255, 255)",
-        "main_heading_color": "rgb(255, 255, 255)",
-        "main_heading_type_color": "rgb(255, 160, 165)",
-        "src_link_color": "rgb(57, 175, 215)",
-        "sidebar_link_color": "rgb(83, 177, 219)",
+        "main_color": "#c5c5c5",
+        "title_color": "#fff",
+        "main_heading_color": "#fff",
+        "main_heading_type_color": "#ffa0a5",
+        "src_link_color": "#39afd7",
+        "sidebar_link_color": "#53b1db",
     },
 )
 call-function: (
     "check-colors",
     {
         "theme": "dark",
-        "main_color": "rgb(221, 221, 221)",
-        "title_color": "rgb(221, 221, 221)",
-        "main_heading_color": "rgb(221, 221, 221)",
-        "main_heading_type_color": "rgb(45, 191, 184)",
-        "src_link_color": "rgb(210, 153, 29)",
-        "sidebar_link_color": "rgb(253, 191, 53)",
+        "main_color": "#ddd",
+        "title_color": "#ddd",
+        "main_heading_color": "#ddd",
+        "main_heading_type_color": "#2dbfb8",
+        "src_link_color": "#d2991d",
+        "sidebar_link_color": "#fdbf35",
     },
 )
 call-function: (
     "check-colors",
     {
         "theme": "light",
-        "main_color": "rgb(0, 0, 0)",
-        "title_color": "rgb(0, 0, 0)",
-        "main_heading_color": "rgb(0, 0, 0)",
-        "main_heading_type_color": "rgb(173, 55, 138)",
-        "src_link_color": "rgb(56, 115, 173)",
-        "sidebar_link_color": "rgb(53, 109, 164)",
+        "main_color": "black",
+        "title_color": "black",
+        "main_heading_color": "black",
+        "main_heading_type_color": "#ad378a",
+        "src_link_color": "#3873ad",
+        "sidebar_link_color": "#356da4",
     },
 )