Fix README to talk about correct Java version

The example tells the buildpack to use version 11, not version 7.

README.md

@@ -21,7 +21,7 @@ The following are _very_ simple examples for deploying the artifact types that w
 * [Spring Boot CLI](docs/example-spring_boot_cli.md)
 
 ## Configuration and Extension
-The buildpack default configuration can be overridden with an environment variable matching the configuration file you wish to override minus the `.yml` extension and with a prefix of `JBP_CONFIG`. It is not possible to add new configuration properties and properties with `nil` or empty values will be ignored by the buildpack (in this case you will have to extend the buildpack, see below). The value of the variable should be valid inline yaml, referred to as "flow style" in the yaml spec ([Wikipedia][] has a good description of this yaml syntax). For example, to change the default version of Java to 7 and adjust the memory heuristics apply this environment variable to the application.
+The buildpack default configuration can be overridden with an environment variable matching the configuration file you wish to override minus the `.yml` extension and with a prefix of `JBP_CONFIG`. It is not possible to add new configuration properties and properties with `nil` or empty values will be ignored by the buildpack (in this case you will have to extend the buildpack, see below). The value of the variable should be valid inline yaml, referred to as "flow style" in the yaml spec ([Wikipedia][] has a good description of this yaml syntax). For example, to change the default version of Java to 11 and adjust the memory heuristics apply this environment variable to the application.
 
 ```bash
 $ cf set-env my-application JBP_CONFIG_OPEN_JDK_JRE '{ jre: { version: 11.+ }, memory_calculator: { stack_threads: 25 } }'