Fixed some doc errors that caused syntax highlighting to fail.
Fixed #5726 -- Documented that inspectdb doesn't detect defaults.
Fixed #4991 -- Emphasized XSS ramifications of help_text not being escaped.
Fixed #23282 -- Corrected inheritance and reverse relations example.

Thanks knowledgepoint-devs for the report and claudep for review.
Fixed #17272 -- Documented that non-editable fields are skipped during model validation.

Thanks mitar for the report.
Fixed #23314 -- Tempered recommendation of storing profile data on custom user.

Thanks gavinwahl for the report.