_content/blog/intro-generics: s/generics is/generics are/
_content/blog/intro-generics: s/generics is/generics are/

Change-Id: I9399ec4d0ce4c5ef5a346b51a11610c743cba091
Reviewed-on: https://go-review.googlesource.com/c/website/+/395614
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@google.com>
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website