Remove no longer necessary Vale steps

What does this MR do?

In !53030 (comment 498492359) I added steps to the Documentation testing page. I needed to follow them to configure the Vale VS Code extension. Today it looks like my extension works properly even if I remove the explicitly added path to vale.ini and the binary. We can instead point at the instructions in the extension Readme.

I also updated the link to Vale Server, as the previous article must have been moved, though I couldn't find it.

Related issues

#300656 (closed)

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