Fix bugs on polaris website (#11556)

### WHAT is this pull request doing?

- [x] Fixes missing icons on `/design` pages
- [x] Removes "Internal only" components landing page from search and
keeps it in the sidebar
- [x] Fixes Legacy Filters image in search results

Author: alex-page

polaris.shopify.com/content/components/deprecated/legacy-filters.mdx

@@ -1,7 +1,7 @@
 ---
 title: Legacy filters
 shortDescription: Legacy version of the Filters component. Used to filter the items of a list or table.
-category: Selection and input
+category: Deprecated
 keywords:
   - filters
   - filtering

polaris.shopify.com/content/design/colors/palettes-and-roles.mdx

@@ -8,7 +8,7 @@ keywords:
   - color use
   - black and white
   - grayscale
-icon: ColorsIcon
+icon: ColorIcon
 ---
 
 # Color → {frontmatter.title}

polaris.shopify.com/content/design/layout/spacial-organization.mdx

@@ -1,7 +1,7 @@
 ---
 title: Spacial organization
 order: 1
-icon: BuyButtonButtonLayoutIcon
+icon: LayoutBuyButtonHorizontalIcon
 keywords:
   - layout
   - layout components

polaris.shopify.com/content/design/typography/font-and-typescale.mdx

@@ -6,7 +6,7 @@ keywords:
   - type styles
   - font sizes
   - fonts
-icon: TextAlignmentLeftIcon
+icon: TextAlignLeftIcon
 hideChildren: true
 order: 1
 ---

polaris.shopify.com/content/design/typography/using-type.mdx

@@ -6,7 +6,7 @@ keywords:
   - type styles
   - font sizes
   - fonts
-icon: TypeIcon
+icon: TextFontIcon
 hideChildren: true
 order: 2
 ---

polaris.shopify.com/pages/api/search/v0/index.tsx

@@ -19,11 +19,11 @@ import {slugify, stripMarkdownLinks} from '../../../../src/utils/various';
 import pages from '../../../../.cache/site';
 
 type IndexablePages = {
-  [K in keyof typeof pages as (typeof pages)[K]['frontMatter'] extends {
+  [K in keyof typeof pages as typeof pages[K]['frontMatter'] extends {
     noIndex: true;
   }
     ? never
-    : K]: (typeof pages)[K];
+    : K]: typeof pages[K];
 };
 
 const searchablePages = Object.fromEntries(
@@ -70,12 +70,17 @@ const getSearchResults = (query?: string) => {
       title,
       description = '',
       category = '',
+      internalOnly,
     } = searchablePages[slug].frontMatter as FrontMatter;
 
     const url = category
       ? `/components/${slugify(category)}/${slugify(title)}`
       : `/components/${slugify(title)}`;
 
+    if (internalOnly) {
+      return;
+    }
+
     results.push({
       id: slugify(`components ${title}`),
       category: 'components',