docs: change a deadlink to an alternative

Katacoda's service no longer exists, an alternative has been used as a
substitution for onboarding members (Killercoda).

Author: JustinZhang17

docs/dev/getting-started/index.md

@@ -16,7 +16,7 @@ Welcome to the team! :)
 |            | <https://www.youtube.com/watch?v=4ht22ReBjno&ab_channel=Deis%2CInc.>         |
 |            | <https://www.youtube.com/watch?v=PziYflu8cB8&ab_channel=Fireship>            |
 
-You can use the interactive learning on [KataCoda](https://www.katacoda.com/statcan), but not completing or understanding everything is alright as long as you have some idea.
+You can use the interactive learning on [Killercoda](https://killercoda.com/), but not completing or understanding everything is alright as long as you have some idea.
 
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