Don't need to specify default project explicitly

Author: philderbeast

cabal-testsuite/PackageTests/ProjectImport/DedupUsingConfigFromSimple/cabal.test.hs

@@ -3,7 +3,7 @@ import Test.Cabal.Prelude
 main = cabalTest . recordMode RecordMarked $ do
   let log = recordHeader . pure
 
-  out <- fails $ cabal' "v2-build" [ "all", "--dry-run", "--project-file=cabal.project" ]
+  out <- fails $ cabal' "v2-build" [ "all", "--dry-run" ]
 
   -- Use assertRegex when the output is tainted by the temp directory, like
   -- this: