fix slack handle

Author: TimidRobot

content/internships/contents.lr

@@ -59,7 +59,7 @@ Here are our mentors for 2021 GSoC:
 
 | Name | Slack Username |
 | ---- | -------------- |
-| Abhishek Naidu | `@Abhishek` |
+| Abhishek Naidu | `@Abhishek Naidu` |
 | [Hugo Solar][authorhugo] | `@hugo` |
 | [Nimish Bongale][authornimish] | `@nimishnb` |
 | [Timid Robot Zehta][authortimidrobot] | `@Timid Robot` |