Tests: add inverse of trait usage test also

Just to be sure it catches unimported traits.

Author: sirbrillig

tests/Sniffs/Imports/RequireImportsSniffTest.php

@@ -96,7 +96,7 @@ public function testRequireImportsSniffCountsTraitUseAsUsage() {
 		$phpcsFile = $helper->prepareLocalFileForSniffs($sniffFile, $fixtureFile);
 		$phpcsFile->process();
 		$lines = $helper->getWarningLineNumbersFromFile($phpcsFile);
-		$expectedLines = [];
+		$expectedLines = [10];
 		$this->assertEquals($expectedLines, $lines);
 	}
 }

tests/Sniffs/Imports/UsedTraitFixture.php

@@ -7,6 +7,7 @@
 
 class Toaster {
 	use Appliance;
+	use UnimportedSymbol; // this should be a warning
 	public function makeToast() {
 		$this->energize();
 	}