[fix] remove dissem.in due to its closure (#4930)

remove dissem.in due to its closure [1]

[1] https://association.dissem.in/dissemin-closure.html

searx/settings.yml

@@ -2771,7 +2771,6 @@ engines:
 doi_resolvers:
   oadoi.org: 'https://oadoi.org/'
   doi.org: 'https://doi.org/'
-  doai.io: 'https://dissem.in/'
   sci-hub.se: 'https://sci-hub.se/'
   sci-hub.st: 'https://sci-hub.st/'
   sci-hub.ru: 'https://sci-hub.ru/'

tests/robot/settings_robot.yml

@@ -51,7 +51,6 @@ engines:
 doi_resolvers:
   oadoi.org: 'https://oadoi.org/'
   doi.org: 'https://doi.org/'
-  doai.io: 'https://dissem.in/'
   sci-hub.se: 'https://sci-hub.se/'
   sci-hub.st: 'https://sci-hub.st/'
   sci-hub.ru: 'https://sci-hub.ru/'