Polish "Disable metrics export in integration tests"

See gh-21658

spring-boot-project/spring-boot-docs/src/docs/asciidoc/production-ready-features.adoc

@@ -1428,6 +1428,13 @@ For example, to disable Datadog:
 	management.metrics.export.datadog.enabled=false
 ----
 
+You can also disable all registries unless stated otherwise by the registry-specific property, as shown in the following example:
+
+[source,properties,indent=0,configprops]
+----
+	management.metrics.export.defaults.enabled=false
+----
+
 Spring Boot will also add any auto-configured registries to the global static composite registry on the `Metrics` class unless you explicitly tell it not to:
 
 [source,properties,indent=0,configprops]

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

@@ -6638,6 +6638,14 @@ include::{test-examples}/jmx/SampleJmxTests.java[tag=test]
 
 
 
+[[boot-features-testing-spring-boot-applications-metrics]]
+==== Using Metrics
+Regardless of your classpath, meter registries, except the in-memory backed, are not auto-configured when using `@SpringBootTest`.
+
+If you need to export metrics to a different backend as part of an integration test, annotate it with `@AutoConfigureMetrics`.
+
+
+
 [[boot-features-testing-spring-boot-applications-mocking-beans]]
 ==== Mocking and Spying Beans
 When running tests, it is sometimes necessary to mock certain components within your application context.