Leaving fsharp:netcore on older image for now

Need newer mono-based fsharp built and published so any issues with netcore can be resolved.

library/fsharp

@@ -10,5 +10,5 @@ Directory: 10.6.0/mono
 Tags: 4, 4.1, 4.1.34
 Directory: 4.1.34/mono
 
-Tags: netcore, 10-netcore, 10.6-netcore, 10.6.0-netcore
-Directory: 10.6.0/netcore
+Tags: netcore, 10-netcore, 10.2-netcore, 10.2.3-netcore
+Directory: 10.2.3/netcore