change extension to .png

Author: Xuelong An Wang

_posts/2023-10-31-sgd.md

@@ -52,6 +52,6 @@ The unanswered questions that follow would include:
     - Most importantly, would more intricately labeled data compensate for low data?
 
 <figure>
-  <img src="/assets/img/structuredgd.png" alt="Sorry, an unanticipated error occured and the image can't load." width="100%" height="auto">
+  <img src="/assets/img/structuredgd.PNG" alt="Sorry, an unanticipated error occured and the image can't load." width="100%" height="auto">
   <figcaption id="sgd"> A (hopefully) cool logo of SGD</figcaption>
 </figure>