bug #16498 fix unused variable warning (eventhorizonpl)

This PR was squashed before being merged into the 2.8 branch (closes #16498).

Discussion
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fix unused variable warning

Hi,

This PR fixes a bug in ClockMock class.

Best regards,
Michal

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Commits
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cf28474 fix unused variable warning

src/Symfony/Bridge/PhpUnit/ClockMock.php

@@ -66,7 +66,7 @@ class ClockMock
             return self::$now;
         }
 
-        return sprintf("%0.6f %d\n", $now - (int) $now, (int) self::$now);
+        return sprintf("%0.6f %d\n", self::$now - (int) self::$now, (int) self::$now);
     }
 
     public static function register($class)