Fix Multi-line TextBox Bug (#1640 ) (#1680)

* Add Disabled ComboBox with Hint to Demo

* Change Line to Path of DashedLine in ComboBox Template

* Delete Trigger of Height of TextBox

* revert "Delete Trigger of Height of TextBox"

* Delete Trigger of Height of TextBox

Author: soi013

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.TextBox.xaml

@@ -212,13 +212,6 @@
                             <Setter TargetName="PART_ContentHost" Property="Margin" Value="0,0,0,8" />
                             <Setter TargetName="Hint" Property="Margin" Value="0,0,0,0" />
                         </MultiTrigger>
-                        <MultiTrigger>
-                            <MultiTrigger.Conditions>
-                                <Condition Property="wpf:TextFieldAssist.HasOutlinedTextField" Value="False" />
-                                <Condition Property="wpf:TextFieldAssist.HasFilledTextField" Value="False" />
-                            </MultiTrigger.Conditions>
-                            <Setter TargetName="PART_ContentHost" Property="Height" Value="{Binding Height, RelativeSource={RelativeSource TemplatedParent}}" />
-                        </MultiTrigger>
                         <MultiTrigger>
                             <MultiTrigger.Conditions>
                                 <Condition Property="AcceptsReturn" Value="true" />
@@ -254,13 +247,6 @@
                             </MultiTrigger.Conditions>
                             <Setter TargetName="HintWrapper" Property="Opacity" Value="1" />
                         </MultiTrigger>
-                        <MultiTrigger>
-                            <MultiTrigger.Conditions>
-                                <Condition Property="wpf:TextFieldAssist.HasOutlinedTextField" Value="False" />
-                                <Condition Property="wpf:TextFieldAssist.HasFilledTextField" Value="False" />
-                            </MultiTrigger.Conditions>
-                            <Setter TargetName="PART_ContentHost" Property="Height" Value="{Binding Height, RelativeSource={RelativeSource TemplatedParent}}" />
-                        </MultiTrigger>
                         <MultiTrigger>
                             <MultiTrigger.Conditions>
                                 <Condition Property="AcceptsReturn" Value="true" />