Update index.html

public/index.html

@@ -382,7 +382,7 @@
         <a id="rgc_backtotop" href="#">Back to top</a>
       </p>
       <p> 
-        <img src="imgs/grey_dot.svg" alt="" width="32px"> <!---  FGDI TODO: to change ugl -->
+        <img src="imgs/grey_dot.png" alt="" width="32px"> <!---  FGDI TODO: to change ugl -->
         Research Group Digitalisation and Information Management @HFT Stuttgart, 2020 - <span id="current-year"></span>.</p>  <!---  FGDI TODO: to change the name of the group or to find aanother abbreviation-->
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