update index.html to match README.md

Former-commit-id: 50e1095cec6db379edbed49434e6460f02c6bf65

index.html

@@ -16,7 +16,7 @@
 
 <figure>
 <img src="libigl-teaser.png" alt="" />
-<figcaption></figcaption></figure>
+</figure>
 
 <p><a href="https://github.com/libigl/libigl/">https://github.com/libigl/libigl/</a></p>