Update seminar.md

seminar.md

@@ -50,8 +50,8 @@ and a mattermost channel for chat. To join the mattermost channel:
 
 |Date|Speaker|Title/Topic|
 |----|-------|-----------|
-|2021-07-05| ? | ? |
-|2021-06-07| ? | ? |
+|2021-07-05| ? | summer break |
+|2021-06-07| ? | summer break |
 |2021-05-10| Anton Lorenzen | A type system for natural language ([slides](https://nc.kwarc.info/s/piPmS9rzJar2bkB)) |
 |2021-04-12| Deyan Ginev | Scientific Statement Classification over arXiv.org ([slides](https://prodg.org/talks/scientific_statement_classification#1)) |
 |2021-03-29| André Greiner-Petter | Comparative Verification of Digital Mathematical Libraries and Computer Algebra Systems ([slides](https://gist.github.com/AndreG-P/4fdbd42f313d112c888c10c2136a3620)) |