Update JavaScriptEncoder.xml (#3722)

Author: joshlang

xml/System.Text.Encodings.Web/JavaScriptEncoder.xml

@@ -179,7 +179,7 @@
 
 Unlike the <xref:System.Text.Encodings.Web.JavaScriptEncoder.Default> encoder, this encoder instance does not escape HTML-sensitive characters such as &lt;, &gt;, &amp;. As a result, it must be used cautiously; for example, it can be used if the output data is within a response whose content-type is known with a charset set to UTF-8.
 
-Unlike the <xref:System.Text.Encodings.Web.JavaScriptEncoder.Default> encoding, the quotation mark is encoded as \" rather than \u0022.
+Unlike the <xref:System.Text.Encodings.Web.JavaScriptEncoder.Default> encoding, the quotation mark is encoded as \\" rather than \u0022.
 
 Unlike the <xref:System.Text.Encodings.Web.JavaScriptEncoder.Default> encoding (which only allows <xref:System.Text.Unicode.UnicodeRanges.BasicLatin?displayProperty=nameWithType>), using this encoder instance allows <xref:System.Text.Unicode.UnicodeRanges.All?displayProperty=nameWithType> to go through unescaped.