cli: remove duplicate global styles from app template

packages/cli/templates/default-app/packages/app/src/App.tsx

@@ -1,26 +1,7 @@
-import { makeStyles } from '@material-ui/core';
 import { createApp } from '@backstage/core';
 import React, { FC } from 'react';
 import * as plugins from './plugins';
 
-const useStyles = makeStyles(theme => ({
-  '@global': {
-    html: {
-      height: '100%',
-      fontFamily: theme.typography.fontFamily,
-    },
-    body: {
-      height: '100%',
-      fontFamily: theme.typography.fontFamily,
-      'overscroll-behavior-y': 'none',
-    },
-    a: {
-      color: 'inherit',
-      textDecoration: 'none',
-    },
-  },
-}));
-
 const app = createApp({
   plugins: Object.values(plugins),
 });
@@ -29,15 +10,12 @@ const AppProvider = app.getProvider();
 const AppRouter = app.getRouter();
 const AppRoutes = app.getRoutes();
 
-const App: FC<{}> = () => {
-  useStyles();
-  return (
-    <AppProvider>
-      <AppRouter>
-        <AppRoutes />
-      </AppRouter>
-    </AppProvider>
-  );
-};
+const App: FC<{}> = () => (
+  <AppProvider>
+    <AppRouter>
+      <AppRoutes />
+    </AppRouter>
+  </AppProvider>
+);
 
 export default App;