Revert some requirements

Native type for storing TimeSpans can be promoted to better precision
later on, so let the problem be uncovered

Author: alex-kulakov

Orm/Xtensive.Orm.Tests/Issues/Issue0818_NanosecondTrancation.cs

@@ -42,7 +42,7 @@ protected override DomainConfiguration BuildConfiguration()
     [Test]
     public void MainTest()
     {
-      Require.ProviderIsNot(StorageProvider.PostgreSql | StorageProvider.Oracle); // PostgreSql and Oracle store intervals with microseconds only
+      Require.ProviderIsNot(StorageProvider.PostgreSql); // PostgreSql stores intervals with microseconds only
 
       long ticks = 123456789;
 

Orm/Xtensive.Orm.Tests/Issues/IssueJira0449_TimeSpanMinMaxValue.cs

@@ -38,8 +38,6 @@ protected override DomainConfiguration BuildConfiguration()
     [Test]
     public void MinTest()
     {
-      Require.ProviderIsNot(StorageProvider.Oracle, "Oracle has no resolution for TimeSpan.MinValue");
-
       using (var session = Domain.OpenSession())
       using (var tx = session.OpenTransaction()) {
         var created = new EntityWithTimeSpan {Value = TimeSpan.MinValue};