Fix docs for loading ORM plugins

[derrickmehaffy]

Description of what you did:

fixes #7339

Adjusted docs to remove the require that would throw errors trying to load bookshelf plugins.

[codecov]

Codecov Report

Merging #7356 into documentation will increase coverage by 7.03%.
The diff coverage is n/a.

@@                Coverage Diff                @@
##           documentation    #7356      +/-   ##
=================================================
+ Coverage          19.14%   26.17%   +7.03%     
=================================================
  Files                855     1130     +275     
  Lines              11933    15414    +3481     
  Branches            1898     2439     +541     
=================================================
+ Hits                2284     4034    +1750     
- Misses              8100     9561    +1461     
- Partials            1549     1819     +270     

Flag	Coverage Δ
#front	18.27% <ø> (+3.78%)	⬆️
#unit	52.96% <ø> (+13.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/strapi-plugin-email/admin/src/pluginId.js	0.00% <0.00%> (-100.00%)	⬇️
...n/src/containers/NotificationProvider/constants.js	0.00% <0.00%> (-100.00%)	⬇️
...i-admin/admin/src/containers/SettingsPage/index.js	0.00% <0.00%> (-66.67%)	⬇️
...trapi-admin/admin/src/containers/LeftMenu/index.js	5.00% <0.00%> (-61.67%)	⬇️
...n/admin/src/containers/LanguageProvider/reducer.js	0.00% <0.00%> (-61.54%)	⬇️
...in/admin/src/containers/Webhooks/ListView/index.js	0.00% <0.00%> (-42.11%)	⬇️
...in/admin/src/containers/Webhooks/EditView/index.js	0.00% <0.00%> (-38.40%)	⬇️
packages/strapi/lib/services/metrics/index.js	65.00% <0.00%> (-35.00%)	⬇️
...admin/admin/src/components/ContainerFluid/index.js	66.66% <0.00%> (-33.34%)	⬇️
...s/strapi-admin/admin/src/containers/Admin/index.js	63.82% <0.00%> (-15.66%)	⬇️
... and 645 more

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[alexandrebodin]

LGTM