change non-existent links to existing links in every file

[BlueButterflies]

Hi guys, I changed the non-existent links with existing links. These changes are necessary for the correct learning of the examples of the open source contribution.

[ahpook]

Hi @BlueButterflies ! Thanks for another great contribution!
Question: this has a lot of the same changes as #3452 - is that on purpose? I think we can only take one of them but it's hard to tell which is correct.

[BlueButterflies]

Hi @ahpook , If #3451 and #3452 seem the same, they are not, because they have two more different fail files to add to the site. #3451 has "Security best practices for you project" file in Italian language and #3452 has "Security best practices for you project" file in Bulgarian language. I worked on two different branches, one is #3451 where it contains the fail "Security best practices for you project" in Italian language and the correction of the links and more and #3452 where it should contain only the "Security best practices for you project" file in Bulgarian language. I don't know why in the branch with the fail "Security best practices for you project" in Bulgarian language the link changes were also added.

[tomthorogood]

@BlueButterflies Thank you for the added context. It would be helpful if you could please ensure that this PR has only it translations, and #3452 has only bg translations. As it is there also appear to be merge conflicts in both. We'll happily accept this change once the two changes are untangled!