chore(TreeView): Remove the CSS modules feature flag from the TreeView component (#5934)

Author: jonrohan

.changeset/thick-teams-taste.md

@@ -0,0 +1,5 @@
+---
+'@primer/react': minor
+---
+
+Remove the CSS modules feature flag from the TreeView component

packages/react/src/TreeView/TreeView.test.tsx

@@ -4,7 +4,6 @@ import React from 'react'
 import {ThemeProvider} from '../ThemeProvider'
 import type {SubTreeState} from './TreeView'
 import {TreeView} from './TreeView'
-import {FeatureFlags} from '../FeatureFlags'
 
 jest.useFakeTimers()
 
@@ -1651,20 +1650,8 @@ describe('CSS Module Migration', () => {
         <TreeView.Item id="item-3">Item 3</TreeView.Item>
       </TreeView>
     )
-    const FeatureFlagElement = () => {
-      return (
-        <FeatureFlags
-          flags={{
-            primer_react_css_modules_ga: true,
-          }}
-        >
-          <TreeViewTestComponent />
-        </FeatureFlags>
-      )
-    }
 
     // Testing on the second child element because the first child element is visually hidden
     expect(render(<TreeViewTestComponent />).container.children[1]).toHaveClass('test-class-name')
-    expect(render(<FeatureFlagElement />).container.children[1]).toHaveClass('test-class-name')
   })
 })