fix: remove @ mention from readme template as tagging users in README does not work (#49)

Author: FidelusAleksander

markdown-templates/readme/exercise-started.md

@@ -2,7 +2,7 @@
 
 <img src="https://octodex.github.com/images/Professortocat_v2.png" align="right" height="200px" />
 
-Hey @{{ login }}!
+Hey {{ login }}!
 
 Mona here. I'm done preparing your exercise. Hope you enjoy! 💚