revert database update ef core code example

Example 1: ef remove migration

/*to remove the last migration:*/
/*Visual Studio:*/
Remove-Migration
/*.Net Core CLI:*/
dotnet ef migrations remove

Example 2: The migration '20200806160941_InitialMigration' has already been applied to the database. Revert it and try again. If the migration has been applied to other databases, consider reverting its changes using a new migration.

dotnet ef database update 0
dotnet ef migrations remove