Clean line breaks in configuration metadata descriptions.

Closes gh-13601

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/TypeUtils.java

@@ -142,6 +142,7 @@ class TypeUtils {
 		String javadoc = (element != null
 				? this.env.getElementUtils().getDocComment(element) : null);
 		if (javadoc != null) {
+			javadoc = javadoc.replaceAll("\\n", "");
 			javadoc = javadoc.trim();
 		}
 		return ("".equals(javadoc) ? null : javadoc);