Update migration.rst

[gpetraroli]

Change return type of handleRequest to void

[OskarStark]

Should target 5.4 branch, right?

[gpetraroli]

Only 6.3 doc is concerned I think

[artyuum]

@gpetraroli there is another type error here (in case you want to fix that as well), the function return type is set as string but it's not returning anything:

symfony-docs/migration.rst

Lines 463 to 473 in b3d1030

	return new StreamedResponse(
	function () use ($requestPath, $legacyScript): string {
	$_SERVER['PHP_SELF'] = $requestPath;
	$_SERVER['SCRIPT_NAME'] = $requestPath;
	$_SERVER['SCRIPT_FILENAME'] = $legacyScript;
	chdir(dirname($legacyScript));
	require $legacyScript;
	}
	);

[gpetraroli]

Thank you, I will

[javiereguiluz]

Thanks Giuseppe and congrats on your first Symfony Docs contribution 🎉