Remove the validation links from .lycheeignore once they are fixed #97

#96 adds .lycheeignore so that the link check passes. The file lists links that are broken in the docs of SpineEventEngine/validation, which this site imports as a module. Only that repository can fix them, and SpineEventEngine/validation#340 tracks the fix.

Once SpineEventEngine/validation#340 is fixed:

1. Update the module to the fixed version in docs/_preview/go.mod and docs/go.mod. In docs/_preview, run hugo mod get -u github.com/SpineEventEngine/validation/docs.
2. Remove the patterns of the fixed links from .lycheeignore. Delete the file if no pattern is left.
3. Check that the check-links job passes.

The pattern for embed-code-go/tree/master/bin can go with the next module update. Validation's master has already fixed those links.

Some background: until #96, the theme inlined jQuery into every page, and Lychee extracted no links past it. It found 7 unique links on the 95 preview pages, so these broken links went unnoticed. It now reads whole pages and finds 794.