Fix old slugs for gridless changes

[rfrenchseti]

• Fixes #N/A
• Were any Django, import pipeline, or table_schema files modified? Y
• Were any JavaScript or CSS files modified? N
  • If YES:
  • JSHINT run on all affected files: Y/NA
  • Tested on Chrome, Firefox, Safari, Edge, and iOS: Y/NA (Remember to test all browser sizes)
  • Tested for race conditions (with delayed API calls if applicable): Y/NA
• Was the documentation reviewed for necessary changes or additions? Y
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Description of changes:

During the earlier change to gridless columns #1331 a couple of things were missed. First, the API Guide needed to be updated. Second, bookmarked URLs that referred to the gridless columns would no longer work. I have changed the old_slug field of the "1" version to be the original slug so that if someone had SURFACEGEOrhea_centerphaseangle in their URL it will be converted to SURFACEGEOrhea_centerphaseangle1 (the "Min" field), which should be good enough. Note that since we only support one old slug, any really old URLs that still use the previous old slug will now fail, but that should be OK since that change happened years ago.

Known problems:

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (b4e40ee) to head (64412dd).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1353 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 41 41 Lines 25001 25001 Branches 1217 1217 ========================================= Hits 25001 25001 ```

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