Update fsharp to 4.1.28 and mono 5.2.

library/fsharp

@@ -2,9 +2,9 @@ Maintainers: Dave Curylo <[email protected]> (@ninjarobot),
              Steve Desmond <[email protected]> (@stevedesmond-ca)
 GitRepo: https://github.com/fsprojects/docker-fsharp.git
 
-Tags: latest, 4, 4.1, 4.1.25
-GitCommit: 96cd7752113e7b4e32fbd6437600816f4b361994
-Directory: 4.1.25/mono
+Tags: latest, 4, 4.1, 4.1.28
+GitCommit: 58be3b5a99a5170b8277c60c77cf163ce66a733f
+Directory: 4.1.28/mono
 
 Tags: 4.1.18
 GitCommit: ad4c4d67a1975b2b0ff0acc49dc46b3271836831