Rename Micrometer Clock bean: clock -> micrometerClock

Closes gh-10436

spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/simple/SimpleExportConfiguration.java

@@ -45,7 +45,7 @@ public class SimpleExportConfiguration {
 
 	@Bean
 	@ConditionalOnMissingBean
-	public Clock clock() {
+	public Clock micrometerClock() {
 		return Clock.SYSTEM;
 	}