Fix typo in documentation

Closes gh-3077

Author: joshthornhill

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -51,7 +51,7 @@ such as the user that launched the application.
 === Customizing the Banner
 The banner that is printed on start up can be changed by adding a `banner.txt` file
 to your classpath, or by setting `banner.location` to the location of such a file.
-If the file has an unusual encoding you can set `banner.encoding` (default is `UTF-8`).
+If the file has an unusual encoding you can set `banner.charset` (default is `UTF-8`).
 
 You can use the following variables inside your `banner.txt` file: