[guides] 4.2 release notes: added technical details for Adequate Record
Improve environment config templates consistency:

* Fix long lines;
* Use simple quotes for string literals when interpolation is not used.
Merge pull request #16841 from tjouan/environment-config-consistency

Improve environment config templates consistency
Merge pull request #16844 from zerothabhishek/master

[guides] 4.2 release notes: added technical details for Adequate Record
pg, correctly dump foreign keys targeting tables in a different schema.

Closes #16907.

[Matthew Draper & Yves Senn]
unify wording in Active Record CHANGELOG. [ci skip]
do not dump foreign keys for ignored tables.
ruby-head should be green

Ruby 2.2 is near to be released so we should support it properly