Fix the wrong documentation about config.autoload_paths [ci skip]
Related to f1af967. [ci skip]
config.autoload_paths is not changeable from environment specific configuration files.
…-support Document that partial indexes are only supported by Postgres and SQLite.
We should document current behavior, and this is design of API for now. Closes #17597
Thanks for patch @sgrif Closes #18216
Documentation is giving an example that can be replaced by a more dry command. Give a hint that ids can be used instead of pluck(:id).
[skip ci] Fix counter_cache in the Rails Guides
Error message no longer tells you to set the (deprecated) secret_token.