[ci skip] Document read_encrypted_secrets config.
[ci skip] Document read_encrypted_secrets config.

Mostly just that it's there.

Closes #28193.

Edouard-chin/rails,assain/rails,hanystudy/rails,matrinox/rails,georgeclaghorn/rails,marklocklear/rails,odedniv/rails,deraru/rails,flanger001/rails,riseshia/railsguides.kr,mechanicles/rails,yalab/rails,tjschuck/rails,kamipo/rails,flanger001/rails,rossta/rails,assain/rails,notapatch/rails,shioyama/rails,Vasfed/rails,palkan/rails,kmayer/rails,mtsmfm/railstest,Erol/rails,eileencodes/rails,xlymian/rails,EmmaB/rails-1,gfvcastro/rails,yalab/rails,illacceptanything/illacceptanything,kaspth/rails,georgeclaghorn/rails,Envek/rails,Stellenticket/rails,schuetzm/rails,tgxworld/rails,aditya-kapoor/rails,BlakeWilliams/rails,bradleypriest/rails,travisofthenorth/rails,mijoharas/rails,repinel/rails,riseshia/railsguides.kr,kddeisz/rails,schuetzm/rails,gauravtiwari/rails,arunagw/rails,kmcphillips/rails,ledestin/rails,bogdanvlviv/rails,assain/rails,matrinox/rails,samphilipd/rails,illacceptanything/illacceptanything,joonyou/rails,kmayer/rails,utilum/rails,tjschuck/rails,jeremy/rails,matrinox/rails,lucasmazza/rails,kaspth/rails,Vasfed/rails,rails/rails,georgeclaghorn/rails,hanystudy/rails,gfvcastro/rails,Stellenticket/rails,notapatch/rails,BlakeWilliams/rails,kddeisz/rails,palkan/rails,aditya-kapoor/rails,xlymian/rails,yalab/rails,mijoharas/rails,iainbeeston/rails,gfvcastro/rails,printercu/rails,samphilipd/rails,pvalena/rails,bogdanvlviv/rails,prathamesh-sonpatki/rails,Stellenticket/rails,jeremy/rails,yawboakye/rails,kmcphillips/rails,repinel/rails,bogdanvlviv/rails,fabianoleittes/rails,gfvcastro/rails,lucasmazza/rails,yahonda/rails,lcreid/rails,maicher/rails,MSP-Greg/rails,Erol/rails,brchristian/rails,illacceptanything/illacceptanything,baerjam/rails,repinel/rails,MSP-Greg/rails,yasslab/railsguides.jp,prathamesh-sonpatki/rails,iainbeeston/rails,mtsmfm/railstest,yahonda/rails,mtsmfm/railstest,deraru/rails,esparta/rails,ttanimichi/rails,flanger001/rails,kmayer/rails,lucasmazza/rails,felipecvo/rails,eileencodes/rails,odedniv/rails,untidy-hair/rails,ngpestelos/rails,tgxworld/rails,joonyou/rails,EmmaB/rails-1,Edouard-chin/rails,alecspopa/rails,aditya-kapoor/rails,betesh/rails,notapatch/rails,yawboakye/rails,illacceptanything/illacceptanything,illacceptanything/illacceptanything,mechanicles/rails,fabianoleittes/rails,ngpestelos/rails,yawboakye/rails,illacceptanything/illacceptanything,rafaelfranca/omg-rails,samphilipd/rails,illacceptanything/illacceptanything,hanystudy/rails,yawboakye/rails,Sen-Zhang/rails,pvalena/rails,kamipo/rails,starknx/rails,vipulnsward/rails,Envek/rails,rossta/rails,kamipo/rails,brchristian/rails,georgeclaghorn/rails,Spin42/rails,jeremy/rails,baerjam/rails,felipecvo/rails,yhirano55/rails,tjschuck/rails,kmcphillips/rails,EmmaB/rails-1,tjschuck/rails,ledestin/rails,ledestin/rails,mechanicles/rails,yahonda/rails,utilum/rails,vipulnsward/rails,pvalena/rails,shioyama/rails,ttanimichi/rails,ttanimichi/rails,lcreid/rails,palkan/rails,starknx/rails,koic/rails,esparta/rails,printercu/rails,schuetzm/rails,Envek/rails,fabianoleittes/rails,joonyou/rails,illacceptanything/illacceptanything,mathieujobin/reduced-rails-for-travis,yasslab/railsguides.jp,rails/rails,BlakeWilliams/rails,Vasfed/rails,kddeisz/rails,vipulnsward/rails,utilum/rails,bradleypriest/rails,eileencodes/rails,jeremy/rails,mohitnatoo/rails,Sen-Zhang/rails,esparta/rails,mijoharas/rails,yahonda/rails,bogdanvlviv/rails,koic/rails,mechanicles/rails,printercu/rails,illacceptanything/illacceptanything,kaspth/rails,MSP-Greg/rails,schuetzm/rails,tgxworld/rails,Stellenticket/rails,kirs/rails-1,arunagw/rails,deraru/rails,eileencodes/rails,yasslab/railsguides.jp,pschambacher/rails,lcreid/rails,flanger001/rails,prathamesh-sonpatki/rails,untidy-hair/rails,arunagw/rails,rails/rails,yalab/rails,lcreid/rails,betesh/rails,mohitnatoo/rails,kmcphillips/rails,gauravtiwari/rails,illacceptanything/illacceptanything,pschambacher/rails,mohitnatoo/rails,alecspopa/rails,rafaelfranca/omg-rails,illacceptanything/illacceptanything,yhirano55/rails,rossta/rails,Sen-Zhang/rails,shioyama/rails,MSP-Greg/rails,yhirano55/rails,illacceptanything/illacceptanything,kddeisz/rails,iainbeeston/rails,prathamesh-sonpatki/rails,mohitnatoo/rails,marklocklear/rails,gcourtemanche/rails,koic/rails,mathieujobin/reduced-rails-for-travis,felipecvo/rails,Erol/rails,rails/rails,notapatch/rails,mathieujobin/reduced-rails-for-travis,iainbeeston/rails,alecspopa/rails,Edouard-chin/rails,pschambacher/rails,baerjam/rails,brchristian/rails,rafaelfranca/omg-rails,marklocklear/rails,bradleypriest/rails,travisofthenorth/rails,betesh/rails,xlymian/rails,aditya-kapoor/rails,joonyou/rails,esparta/rails,untidy-hair/rails,utilum/rails,illacceptanything/illacceptanything,gcourtemanche/rails,maicher/rails,assain/rails,maicher/rails,repinel/rails,travisofthenorth/rails,Vasfed/rails,odedniv/rails,gcourtemanche/rails,pvalena/rails,palkan/rails,kirs/rails-1,illacceptanything/illacceptanything,riseshia/railsguides.kr,tgxworld/rails,arunagw/rails,untidy-hair/rails,yasslab/railsguides.jp,vipulnsward/rails,BlakeWilliams/rails,Edouard-chin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