Avoid string concatenation inside StringBuilder append()

See gh-15589

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/UnresolvedDependenciesAnalyzer.java

@@ -52,11 +52,11 @@ class UnresolvedDependenciesAnalyzer {
 			StringBuilder message = new StringBuilder();
 			message.append("\nDuring the build, one or more dependencies that were "
 					+ "declared without a version failed to resolve:\n");
-			this.dependenciesWithNoVersion
-					.forEach((dependency) -> message.append("    " + dependency + "\n"));
+			this.dependenciesWithNoVersion.forEach((dependency) -> message.append("    ")
+					.append(dependency).append("\n"));
 			message.append("\nDid you forget to apply the "
-					+ "io.spring.dependency-management plugin to the " + project.getName()
-					+ " project?\n");
+					+ "io.spring.dependency-management plugin to the ");
+			message.append(project.getName()).append(" project?\n");
 			logger.warn(message.toString());
 		}
 	}