MaskedTextBox.PasswordChar update remark for disabling (#10696)

Author: kanilsz

xml/System.Windows.Forms/MaskedTextBox.xml

@@ -2447,7 +2447,7 @@
           <format type="text/markdown"><![CDATA[
 
 ## Remarks
- For sensitive user input, it is common practice to conceal the actual information entered by the user. If the <xref:System.Windows.Forms.MaskedTextBox.PasswordChar%2A> property is set to a non-null character, <xref:System.Windows.Forms.MaskedTextBox> will display this character for all input into the control. Setting this property to `null` will disable this functionality.
+ For sensitive user input, it is common practice to conceal the actual information entered by the user. If the <xref:System.Windows.Forms.MaskedTextBox.PasswordChar%2A> property is set to a non-null character, <xref:System.Windows.Forms.MaskedTextBox> will display this character for all input into the control. Setting this property to `\0` will disable this functionality.
 
  If you want to use the operating system supplied password character, which is defined in COMCTL32.dll, use the <xref:System.Windows.Forms.MaskedTextBox.UseSystemPasswordChar%2A> property instead. If both the <xref:System.Windows.Forms.MaskedTextBox.PasswordChar%2A> and <xref:System.Windows.Forms.MaskedTextBox.UseSystemPasswordChar%2A> properties are activated, the latter takes precedence.