Allow Info to be built with null values

Fixes gh-48401

Author: philwebb

module/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/info/Info.java

@@ -105,7 +105,7 @@ public Builder() {
 		 * @param value the detail value
 		 * @return this {@link Builder} instance
 		 */
-		public Builder withDetail(String key, Object value) {
+		public Builder withDetail(String key, @Nullable Object value) {
 			this.content.put(key, value);
 			return this;
 		}