fix: update incorrect link

The old link "How does Ethereum work, anyway?" in the "FURTHER READING" section of the "Intro to Ethereum" page is no longer accessible, because the domain "preethikasireddy.com" expired a long time.

Now this link is replaced with the correct link to this article hosted on medium.com.

This PR has been discussed in this issue
ethereum#13209

public/content/developers/docs/intro-to-ethereum/index.md

@@ -107,7 +107,7 @@ A reusable snippet of code (a program) which a developer publishes into EVM stat
 ## Further reading {#further-reading}
 
 - [Ethereum Whitepaper](/whitepaper/)
-- [How does Ethereum work, anyway?](https://www.preethikasireddy.com/post/how-does-ethereum-work-anyway) - _Preethi Kasireddy_ (**NB** this resource is still valuable but be aware that it predates [The Merge](/roadmap/merge) and therefore still refers to Ethereum's proof-of-work mechanism - Ethereum is actually now secured using [proof-of-stake](/developers/docs/consensus-mechanisms/pos))
+- [How does Ethereum work, anyway?](https://preethikasireddy.medium.com/how-does-ethereum-work-anyway-22d1df506369) - _Preethi Kasireddy_ (**NB** this resource is still valuable but be aware that it predates [The Merge](/roadmap/merge) and therefore still refers to Ethereum's proof-of-work mechanism - Ethereum is actually now secured using [proof-of-stake](/developers/docs/consensus-mechanisms/pos))
 
 _Know of a community resource that helped you? Edit this page and add it!_