minor grammar correction

21.md

@@ -43,7 +43,7 @@ Even if you don’t want/need certs, the outline of the topics in these referenc
 
 Steve (@snori74) was a collector of postcards and enjoyed greatly all the "Snail Mail" he received from the students.
 
-But since [his passing](https://www.reddit.com/r/linuxupskillchallenge/comments/mki3uw/rest_in_peace_snori74/) there's nowhere to send postcards anymore. You can show your appeciation for the course by letting everyone else know how awesome it was! Show your the world you finished the challenge by posting on [twitter](https://twitter.com/compose/tweet/?text=Hey%21%20I%20just%20finished%20the%20%23LinuxUpskillChallenge at https%3A%2F%2Fwww.reddit.com%2Fr%2Flinuxupskillchallenge%2F) and on other social media.
+But since [his passing](https://www.reddit.com/r/linuxupskillchallenge/comments/mki3uw/rest_in_peace_snori74/) there's nowhere to send postcards anymore. You can show your appeciation for the course by letting everyone else know how awesome it was! Show the world you finished the challenge by posting on [twitter](https://twitter.com/compose/tweet/?text=Hey%21%20I%20just%20finished%20the%20%23LinuxUpskillChallenge at https%3A%2F%2Fwww.reddit.com%2Fr%2Flinuxupskillchallenge%2F) and on other social media.
 
 **Thanks for all and happy linuxing!**