Fix table row rendering in Safari (#998)

# Pull Request

## 🤨 Rationale

Fixes #984 

## 👩‍💻 Implementation

As @rajsite and @msmithNI suggested in the linked issue, use
`this.$fastController.isConnected` instead of `this.isConnected` in the
table cell's `cellTemplateChanged()` method.

## 🧪 Testing

I manually tested in Safari in Storybook and the Angular example app.
Malcolm tested in Playwright's Safari.

Auto tests would be covered by #990.

## ✅ Checklist

<!--- Review the list and put an x in the boxes that apply or ~~strike
through~~ around items that don't (along with an explanation). -->

- [x] I have updated the project documentation to reflect my changes or
determined no changes are needed.

change/@ni-nimble-components-3ed590bf-fbf0-44c2-9c02-b8c3307f7292.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Fix table row rendering on Safari",
+  "packageName": "@ni/nimble-components",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

packages/nimble-components/src/table/components/cell/index.ts

@@ -52,7 +52,7 @@ export class TableCell<
     }
 
     protected cellTemplateChanged(): void {
-        if (this.isConnected) {
+        if (this.$fastController.isConnected) {
             this.customCellView = this.cellTemplate?.render(
                 this.cellState,
                 this.cellContentContainer