Update index.md

Author: mtian8

docs/index.md

@@ -20,7 +20,7 @@
 
 <p align="center">
 * Equal contribution lead authors. † Data curation, alphabetical order.
-‡ Corresponding to: [mtian8](mailto:mtian8@illinois.edu), [haopeng](mailto:haopeng@illinois.edu), [elihu@anl.gov](mailto:elihu@anl.gov)
+‡ Corresponding to: [mtian8](mtian8@illinois.edu), [haopeng](haopeng@illinois.edu), [elihu@anl.gov](elihu@anl.gov)
 
 </p>