Remove obsolete extensions.

Author: Tratcher

src/Microsoft.Extensions.BufferedHtmlContent.Sources/BufferedHtmlContent.cs

@@ -87,7 +87,7 @@ public void WriteTo(TextWriter writer, HtmlEncoder encoder)
                 var entryAsString = entry as string;
                 if (entryAsString != null)
                 {
-                    encoder.Encode(entryAsString, writer);
+                    encoder.Encode(writer, entryAsString);
                 }
                 else
                 {

src/Microsoft.Extensions.WebEncoders/EncoderExtensions.cs

@@ -414,7 +414,7 @@ public UnencodedString(string value)
 
             public void WriteTo(TextWriter writer, HtmlEncoder encoder)
             {
-                encoder.Encode(Value, writer);
+                encoder.Encode(writer, Value);
             }
         }