Update casing

Author: anmolbohra97

articles/event-grid/toc.yml

@@ -137,7 +137,7 @@ items:
             href: communication-services-voice-video-events.md
           - name: Presence Events
             href: communication-services-presence-events.md
-          - name: Email events
+          - name: Email Events
             href: communication-services-email-events.md
         - name: Azure Container Registry
           href: event-schema-container-registry.md