Remove dotnet-db-samples submodule

Author: gvenzl

.gitmodules

@@ -1,9 +1,6 @@
 [submodule "SQL/dw-vldb-samples"]
 	path = sql/dw-vldb-samples
 	url = https://github.com/oracle/dw-vldb-samples
-[submodule ".NET/dotnet-db-samples"]
-	path = dotnet/dotnet-db-samples
-	url = https://github.com/oracle/dotnet-db-samples
 [submodule "Java/jdbc-ucp"]
 	path = java/jdbc-ucp
 	url = https://github.com/oracle/jdbc-ucp