Typo in footer SVG markup

Follow-up to webcompat#2484 due to a silly typo...

r? @miketaylr

Author: patrickhlauke

webcompat/templates/shared/footer.html

@@ -74,7 +74,7 @@
       <ul class="grid-cell x1 footer-sub-icons">
         <li class="footer-icon icon-twitter">
           <a class="footer-item-link" aria-label="open Twitter in a new tab" href="https://twitter.com/webcompat/with_replies" target="_blank">
-              <svg class="icon" role="presentation" viewBox="0 0 30 30 aria-hidden="true"">
+              <svg class="icon" role="presentation" viewBox="0 0 30 30" aria-hidden="true">
                   <use xlink:href="#svg-twitter" />
               </svg>
           </a>