[Text] fix tab width. It's too long

samples/ControlCatalog/Pages/TextBoxPage.xaml

@@ -38,7 +38,7 @@
                  UseFloatingWatermark="True"
                  PasswordChar="*"
                  Text="Password" />
-        <TextBox Width="200" Text="Left aligned text" TextAlignment="Left" />
+        <TextBox Width="200" Text="Left aligned text" TextAlignment="Left" AcceptsTab="True" />
         <TextBox Width="200" Text="Center aligned text" TextAlignment="Center" />
         <TextBox Width="200" Text="Right aligned text" TextAlignment="Right" />
         <TextBox Width="200" Text="Custom selection brush"

src/Avalonia.Base/Media/TextFormatting/TextParagraphProperties.cs

@@ -63,14 +63,11 @@
         {
             get { return 0; }
         }
-        
+
         /// <summary>
         /// Gets the default incremental tab width.
         /// </summary>
-        public virtual double DefaultIncrementalTab
+        public virtual double DefaultIncrementalTab => 0;
-        {
-            get { return 4 * DefaultTextRunProperties.FontRenderingEmSize; }
-        }
 
         /// <summary>
         /// Gets the letter spacing.