[data_visualizer] Migrate deprecated EuiPage* component (#168298)

## Summary

EUI will shortly be removing several deprecated `EuiPage*` components,
and we're updating a few remaining Kibana usages of these deprecated
components ahead of time.

⚠️ PLEASE NOTE: We have **not** QA'd these changes to ensure that the UI
is 1:1 from before. We do not have the domain knowledge or time to spin
up local instances of all plugins with deprecations, and ask that the
CODEOWNING team pull down this branch and QA the affected page(s)
locally to ensure the UI looks like the same as production. ⚠️

See https://github.com/elastic/kibana/issues/161872 for other similar
tasks with more information about this effort.

x-pack/plugins/data_visualizer/public/application/file_data_visualizer/components/import_view/import_view.js

@@ -11,7 +11,7 @@ import React, { Component } from 'react';
 import {
   EuiButton,
   EuiPageBody,
-  EuiPageContentHeader_Deprecated as EuiPageContentHeader,
+  EuiPageHeader,
   EuiPanel,
   EuiSpacer,
   EuiTitle,
@@ -481,11 +481,11 @@ export class ImportView extends Component {
 
     return (
       <EuiPageBody data-test-subj="dataVisualizerPageFileImport">
-        <EuiPageContentHeader>
+        <EuiPageHeader>
           <EuiTitle>
             <h1>{this.props.fileName}</h1>
           </EuiTitle>
-        </EuiPageContentHeader>
+        </EuiPageHeader>
         <EuiSpacer size="m" />
         <EuiPanel data-test-subj="dataVisualizerFileImportSettingsPanel">
           <EuiTitle size="s">