Rename file in index.md

Author: kiranchandramohan

flang/docs/index.md

@@ -29,7 +29,7 @@ on how to get in touch with us and to learn more about the current status.
    GettingInvolved
    GettingStarted
    ImplementingASemanticCheck
-   OpenMPStandardsSupport
+   OpenMPSupport
    PullRequestChecklist
 ```