fix ravendb test hardcoded image tag

Author: digital88

tests/Testcontainers.RavenDb.Tests/RavenDbContainerTest.cs

@@ -28,6 +28,6 @@ public void GetBuildNumberOperationReturnsBuildNumber()
         var buildNumber = documentStore.Maintenance.Server.Send(new GetBuildNumberOperation());
 
         // Then
-        Assert.Equal("5.4", buildNumber.ProductVersion);
+        Assert.Contains(buildNumber.ProductVersion, _ravenDbContainer.Image.Tag);
     }
 }