In User Guide Appendix, update link and name of the Dataverse crosswalk

[jggautier]

In order to move the Dataverse Crosswalk into the Dataverse shared Google Drive, where more of the Dataverse team can maintain it, I had to copy the Google Sheet into a new Google Sheet, and leave a note on the original crosswalk so that others know that it's being maintained in a different Google Sheet with a different URL, https://docs.google.com/spreadsheets/d/1VAhZ83hKURX_4T-bOkn7XCb9h62Gr2gcJI1fWe4Rl4c.

In the User Guide's Appendix page, I think we should update the link so that it points to where the crosswalk lives now.

Old URL: https://docs.google.com/spreadsheets/d/10Luzti7svVTVKTA-px27oq3RxCUM-QbiTkm8iMd5C54
New URL: https://docs.google.com/spreadsheets/d/1VAhZ83hKURX_4T-bOkn7XCb9h62Gr2gcJI1fWe4Rl4c

I changed the name a while back and we should update that in the guides, too, so it matches the name of the doc in the guides.

Old name (that's on the Appendix page as of v6.4): Dataverse Software 4.0 Metadata Crosswalk: DDI, DataCite, DC, DCTerms, VO, ISA-Tab
Name of the crosswalk on the Google Sheet: Dataverse Metadata Crosswalk

I searched in the guides and couldn't find any other pages that use the old URL to the crosswalk. As far as I know, the old URL is only on that User Guide's Appendix page. I imagine that if it's anywhere else, outside of the guides, folks will see that it's been replaced and update their docs.