Fix error on `resource` assertion if message has a second placeholder

[cs278]

Prior to this change code such as Assert::resource(null, 'stream', 'Got: %s, type: %s') would fail as the second placeholder was only passed into sprintf() if the value supplied is a resource.

Test I've added without the code change fails with:

1) Webmozart\Assert\Tests\AssertTest::testResourceOfTypeCustomMessage
Failed asserting that exception of type "ArgumentCountError" matches expected exception "\InvalidArgumentException". Message was: "3 arguments are required, 2 given" at
<snip>/src/Assert.php:255
<snip>/tests/AssertTest.php:827

[cs278]

I came to the conclusion a bespoke test was needed but I might have missed something.

[cs278]

Great to see some activity here again, I've rebased this to pickup the CI changes.

[shadowhand]

Thank you!