String Ref documentation is missed since 1.77.0

[YarikTH]

"String Ref" is listed in the library list on the site https://www.boost.org/doc/libs/
and documentation link redirects to https://www.boost.org/doc/libs/1_82_0/libs/utility/doc/html/string_ref.html

Last version where documentation is found is 1.77.0

https://www.boost.org/doc/libs/1_77_0/libs/utility/doc/html/string_ref.html

[Lastique]

@glenfe Do you know why String Ref is still present in the 1.84 library list (https://www.boost.org/doc/libs/1_84_0/), despite it was removed from metadata in 219ee98 (which shipped in 1.84)? What needs to be done to remove it?

PS: This was reported in #105 before.