drop return type declaration

The configured memory limit can exceed the range that can be represented
by an integer.

src/Symfony/Component/HttpKernel/DataCollector/MemoryDataCollector.php

@@ -93,7 +93,10 @@ class MemoryDataCollector extends DataCollector implements LateDataCollectorInte
         return 'memory';
     }
 
-    private function convertToBytes(string $memoryLimit): int
+    /**
+     * @return int|float
+     */
+    private function convertToBytes(string $memoryLimit)
     {
         if ('-1' === $memoryLimit) {
             return -1;