Retire file map (dotnet#4282)

Author: mingwli

xml/System/String.xml

@@ -99,7 +99,7 @@
 
  A string is a sequential collection of characters that is used to represent text. A <xref:System.String> object is a sequential collection of <xref:System.Char?displayProperty=nameWithType> objects that represent a string; a <xref:System.Char?displayProperty=nameWithType> object corresponds to a UTF-16 code unit. The value of the <xref:System.String> object is the content of the sequential collection of <xref:System.Char?displayProperty=nameWithType> objects, and that value is immutable (that is, it is read-only). For more information about the immutability of strings, see the [Immutability and the StringBuilder class](#Immutability) section later in this topic. The maximum size of a <xref:System.String> object in memory is 2GB, or about 1 billion characters.
 
-For more information about Unicode, UTF-16, code units, code points, and the <xref:System.Char> and <xref:System.Text.Rune> types, see [Introduction to character encoding in .NET](~/docs/dotnet/standard/base-types/character-encoding-introduction.md).
+For more information about Unicode, UTF-16, code units, code points, and the <xref:System.Char> and <xref:System.Text.Rune> types, see [Introduction to character encoding in .NET](/dotnet/standard/base-types/character-encoding-introduction).
 
  In this section:
 
@@ -225,7 +225,7 @@ For more information about Unicode, UTF-16, code units, code points, and the <xr
 
  This example works with text elements by using the <xref:System.Globalization.StringInfo.GetTextElementEnumerator%2A?displayProperty=nameWithType> method and the <xref:System.Globalization.TextElementEnumerator> class to enumerate all the text elements in a string. You can also retrieve an array that contains the starting index of each text element by calling the <xref:System.Globalization.StringInfo.ParseCombiningCharacters%2A?displayProperty=nameWithType> method.
 
- For more information about working with units of text rather than individual <xref:System.Char> values, see [Introduction to character encoding in .NET](~/docs/dotnet/standard/base-types/character-encoding-introduction.md).
+ For more information about working with units of text rather than individual <xref:System.Char> values, see [Introduction to character encoding in .NET](/dotnet/standard/base-types/character-encoding-introduction).
 
 <a name="Nulls"></a>
 ## Null strings and empty strings