Remove uncessary call in PropertiesMigrationReport

Closes gh-14974

spring-boot-project/spring-boot-properties-migrator/src/main/java/org/springframework/boot/context/properties/migrator/PropertiesMigrationReporter.java

@@ -174,7 +174,6 @@ class PropertiesMigrationReporter {
 
 	private Map<String, ConfigurationPropertySource> getPropertySourcesAsMap() {
 		Map<String, ConfigurationPropertySource> map = new LinkedHashMap<>();
-		ConfigurationPropertySources.get(this.environment);
 		for (ConfigurationPropertySource source : ConfigurationPropertySources
 				.get(this.environment)) {
 			map.put(determinePropertySourceName(source), source);