Move property notes up to external configuration section

See gh-35662

spring-boot-project/spring-boot-docs/src/docs/asciidoc/features/external-config.adoc

@@ -37,6 +37,11 @@ Config data files are considered in the following order:
 NOTE: It is recommended to stick with one format for your entire application.
 If you have configuration files with both `.properties` and YAML format in the same location, `.properties` takes precedence.
 
+NOTE: If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (for example, configprop:spring.config.name[format=envvar] instead of configprop:spring.config.name[]).
+See <<features#features.external-config.typesafe-configuration-properties.relaxed-binding.environment-variables>> for details.
+
+NOTE: If your application runs in a servlet container or application server, then JNDI properties (in `java:comp/env`) or servlet context initialization parameters can be used instead of, or as well as, environment variables or system properties.
+
 To provide a concrete example, suppose you develop a `@Component` that uses a `name` property, as shown in the following example:
 
 include::code:MyBean[]
@@ -173,11 +178,6 @@ This search ordering lets you specify default values in one configuration file a
 You can provide default values for your application in `application.properties` (or whatever other basename you choose with `spring.config.name`) in one of the default locations.
 These default values can then be overridden at runtime with a different file located in one of the custom locations.
 
-NOTE: If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (for example, configprop:spring.config.name[format=envvar] instead of configprop:spring.config.name[]).
-See <<features#features.external-config.typesafe-configuration-properties.relaxed-binding.environment-variables>> for details.
-
-NOTE: If your application runs in a servlet container or application server, then JNDI properties (in `java:comp/env`) or servlet context initialization parameters can be used instead of, or as well as, environment variables or system properties.
-
 
 
 [[features.external-config.files.optional-prefix]]