Use parenthesis with single-arg lambdas

Use regular expression search/replace to ensure all single-arg
lambdas have parenthesis. This aligns with the style used in Spring
Boot and ensure that single-arg and multi-arg lambdas are consistent.

Issue gh-8945

samples/boot/hellowebflux/src/test/java/sample/HelloWebfluxApplicationTests.java

@@ -105,10 +105,10 @@ public class HelloWebfluxApplicationTests {
 	}
 
 	private Consumer<HttpHeaders> userCredentials() {
-		return httpHeaders -> httpHeaders.setBasicAuth("user", "user");
+		return (httpHeaders) -> httpHeaders.setBasicAuth("user", "user");
 	}
 
 	private Consumer<HttpHeaders> invalidCredentials() {
-		return httpHeaders -> httpHeaders.setBasicAuth("user", "INVALID");
+		return (httpHeaders) -> httpHeaders.setBasicAuth("user", "INVALID");
 	}
 }