Upgrade to Micrometer 1.6.0

Closes gh-23525

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/elastic/ElasticProperties.java

@@ -37,7 +37,7 @@ public class ElasticProperties extends StepRegistryProperties {
 	/**
 	 * Index to export metrics to.
 	 */
-	private String index = "metrics";
+	private String index = "micrometer-metrics";
 
 	/**
 	 * Index date format used for rolling indices. Appended to the index name.

spring-boot-project/spring-boot-dependencies/build.gradle

@@ -1108,7 +1108,7 @@ bom {
 			]
 		}
 	}
-	library("Micrometer", "1.5.5") {
+	library("Micrometer", "1.6.0") {
 		group("io.micrometer") {
 			modules = [
 				"micrometer-registry-stackdriver" {