Replace deprecated PHPUnit expectExceptionMessage() with expectExceptionObject()

[Copilot]

expectExceptionMessage() is soft-deprecated in PHPUnit 13.2 and scheduled for removal in 15.0. Two usages in InAppPurchasesControllerTest triggered PHPStan warnings.

Changes

• tests/Controller/InAppPurchasesControllerTest.php: Replace both expectException() + expectExceptionMessage() pairs with expectExceptionObject(), using the existing factory methods on ExtensionStoreException:

// Before
$this->expectException(ExtensionStoreException::class);
$this->expectExceptionMessage('The extension with technical name "otherExtension" is not known.');

// After
$this->expectExceptionObject(ExtensionStoreException::unknownExtension('otherExtension'));