Fix a typo in ResponseEntity documentation

Closes gh-28647

src/docs/asciidoc/web/webflux.adoc

@@ -2975,7 +2975,7 @@ configure or customize message writing.
 	public ResponseEntity<String> handle() {
 		String body = ... ;
 		String etag = ... ;
-		return ResponseEntity.ok().eTag(etag).build(body);
+		return ResponseEntity.ok().eTag(etag).body(body);
 	}
 ----
 [source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]

src/docs/asciidoc/web/webmvc.adoc

@@ -3386,7 +3386,7 @@ See <<mvc-ann-jackson>> for details.
 	public ResponseEntity<String> handle() {
 		String body = ... ;
 		String etag = ... ;
-		return ResponseEntity.ok().eTag(etag).build(body);
+		return ResponseEntity.ok().eTag(etag).body(body);
 	}
 ----
 [source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]