Fix doc about running native commands

Closes gh-5829

Author: cristiangreco

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

@@ -415,7 +415,7 @@ From inside the embedded shell you can run other commands directly:
 ----
 
 The embedded shell supports ANSI color output as well as `tab` completion. If you need
-to run a native command you can use the `$` prefix. Hitting `ctrl-c` will exit the
+to run a native command you can use the `!` prefix. Hitting `ctrl-c` will exit the
 embedded shell.