remove draft pattern from patterns index page (#8473)

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### WHY are these changes introduced?

Draft pages should not be visible on the `Pattern Page`. This PR
resolves this.

### WHAT is this pull request doing?

Before: 
![Screenshot 2023-02-23 at 2 02 54
pm](https://user-images.githubusercontent.com/12119389/220812495-87916a64-7f79-4c92-9748-14b6f60bd4e3.png)

After: 
![Screenshot 2023-02-23 at 2 02 45
pm](https://user-images.githubusercontent.com/12119389/220812511-33714fd7-00b3-463a-a97c-73a7e2905dd0.png)

### How to 🎩

🖥 [Local development
instructions](https://github.com/Shopify/polaris/blob/main/README.md#local-development)
🗒 [General tophatting
guidelines](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting.md)
📄 [Changelog
guidelines](https://github.com/Shopify/polaris/blob/main/.github/CONTRIBUTING.md#changelog)

<!--
  Give as much information as needed to experiment with the component
  in the playground.
-->

<details>
<summary>Copy-paste this code in
<code>playground/Playground.tsx</code>:</summary>

```jsx
import React from 'react';
import {Page} from '../src';

export function Playground() {
  return (
    <Page title="Playground">
      {/* Add the code you want to test in here */}
    </Page>
  );
}
```

</details>

### 🎩 checklist

- [ ] Tested on
[mobile](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting.md#cross-browser-testing)
- [ ] Tested on [multiple
browsers](https://help.shopify.com/en/manual/shopify-admin/supported-browsers)
- [ ] Tested for
[accessibility](https://github.com/Shopify/polaris/blob/main/documentation/Accessibility%20testing.md)
- [ ] Updated the component's `README.md` with documentation changes
- [ ] [Tophatted
documentation](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting%20documentation.md)
changes in the style guide

Author: gwyneplaine

.changeset/seven-boxes-punch.md

@@ -0,0 +1,5 @@
+---
+'polaris.shopify.com': patch
+---
+
+Remove draft pattern pages from PatternsPage

polaris.shopify.com/src/components/PatternsPage/index.tsx

@@ -31,18 +31,20 @@ export const PatternsPage = () => (
           />
         </div>
         <Grid>
-          {Object.values(patterns).map(({frontMatter: pattern}, index) => (
-            <GridItem
-              key={index}
-              title={pattern.title}
-              description={pattern.description ?? ''}
-              url={pattern.url ?? ''}
-              renderPreview={() => (
-                <Preview alt={pattern.title} src={pattern.previewImg} />
-              )}
-              status={pattern.status as Status}
-            />
-          ))}
+          {Object.values(patterns)
+            .filter(({frontMatter: {draft}}) => !draft)
+            .map(({frontMatter: pattern}, index) => (
+              <GridItem
+                key={index}
+                title={pattern.title}
+                description={pattern.description ?? ''}
+                url={pattern.url ?? ''}
+                renderPreview={() => (
+                  <Preview alt={pattern.title} src={pattern.previewImg} />
+                )}
+                status={pattern.status as Status}
+              />
+            ))}
         </Grid>
       </Stack>
     </Page>