Clarify wildcard usage to select input files with Java configuration

Resolves #4707

Signed-off-by: Mahmoud Ben Hassine <mbenhassine@vmware.com>

spring-batch-docs/modules/ROOT/pages/readers-and-writers/multi-file-input.adoc

@@ -24,10 +24,10 @@ The following example shows how to read files with wildcards in Java:
 [source, java]
 ----
 @Bean
-public MultiResourceItemReader multiResourceReader() {
+public MultiResourceItemReader multiResourceReader(@Value("classpath:data/input/file-*.txt") Resource[] resources) {
 	return new MultiResourceItemReaderBuilder<Foo>()
 					.delegate(flatFileItemReader())
-					.resources(resources())
+					.resources(resources)
 					.build();
 }
 ----