[css-values-4] Broken link in CSS Values and Units Module Level 4

[dontcallmedom-bot]

While crawling CSS Values and Units Module Level 4, the following links to other specifications were detected as pointing to non-existing anchors, which should be fixed:

• http://www.w3.org/TR/css-values-3/#acknowledgements

_{This issue was detected and reported semi-automatically by Strudy based on data collected in webref.}