Replace usage of deprecated PHPUnit returnCallback() function (#2085)

This PR is meant to serve as a first step for addressing changes that
will need to be made before #1866
can be merged. The PHPUnit function `returnCallback()` is
[deprecated](sebastianbergmann/phpunit#5423),
so our usage of it was switched to its shorthand syntax, as recommended
by the docs.

app/cdash/include/Test/CDashTestCase.php

@@ -82,10 +82,9 @@ protected function setDatabaseMocked()
         $mock_pdo
             ->expects($this->any())
             ->method('quote')
-            ->will($this->returnCallback(function ($arg) {
+            ->willReturnCallback(function ($arg) {
                 return "'" . $arg . "'";
-            })
-            );
+            });
 
         Database::setInstance(Database::class, $mock_pdo);
     }

phpstan-baseline.neon

@@ -12411,11 +12411,6 @@ parameters:
 			count: 4
 			path: app/cdash/include/Test/CDashTestCase.php
 
-		-
-			message: "#^Dynamic call to static method PHPUnit\\\\Framework\\\\TestCase\\:\\:returnCallback\\(\\)\\.$#"
-			count: 1
-			path: app/cdash/include/Test/CDashTestCase.php
-
 		-
 			message: "#^Method CDash\\\\Test\\\\CDashTestCase\\:\\:createMockFromBuilder\\(\\) has no return type specified\\.$#"
 			count: 1