title: How to get rid of shadows in the Material-UI theme
body: <p>I need to get rid of shadows in MuiPaper component.</p>
  
  <p>I found some solution:
  <a href="https://stackoverflow.com/questions/50516398/material-ui-the-shadows-array-provided-to-createmuitheme-should-support-25-elev">for example</a></p>
  
  <p>but they didn't work. 
  I can override only root component (MuiPaper) but the shadow is set by the class MuiPaper-elevation1-24.</p>
  
  <p>code that render component </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>const List = props =&gt; (
    &lt;List {...props} title="lists" filters={&lt;Filter /&gt;} sort={{ field: 'timestamps.createdAt', order: 'DESC' }}&gt;
      &lt;Datagrid rowClick="show" expand={&lt;Edit /&gt;} &gt;
        &lt;TextField source="attributes.campaignUuid" label="Campaign Uuid" /&gt;
        &lt;TextField source="attributes.affiliateId" label="Affiliate Id" /&gt;
        &lt;DateField source="attributes.createdAt" label="Created At" showTime locales="ru-RU" sortBy="timestamps.createdAt" /&gt;
        &lt;DateField source="attributes.updatedAt" label="Updated At" showTime locales="ru-RU" sortBy="timestamps.updatedAt" /&gt;
        &lt;DeleteButton /&gt;
      &lt;/Datagrid&gt;
    &lt;/List&gt;
  );</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>And HTML that I receive: 
  
  &lt;div class="list-page Component-root-904"&gt;
    &lt;div class="MuiPaper-root-21 MuiPaper-elevation1-24 MuiPaper-rounded-22 MuiCard-root-740 Component-card-905"&gt;&lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>