Set version to 0.6.8

Author: github-actions[bot]

Project.toml

@@ -1,7 +1,7 @@
 name = "GeometricProblems"
 uuid = "18cb22b4-ad41-5c80-9c5f-710df63fbdc9"
 authors = ["Michael Kraus <michael.kraus@ipp.mpg.de>"]
-version = "0.6.7"
+version = "0.6.8"
 
 [deps]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"