FYI: it might be better to search by port:23

https://www.shodan.io/search?query=port%3A23

Or to filter by product:telnetd

https://www.shodan.io/search?query=product%3Atelnetd

A query of "telnet" searches Shodan for banners where the "data" property contains the string "telnet":

https://book.shodan.io/getting-started/query-syntax/