added new relative path

tests/ImageSharp.Tests/TestFile.cs

@@ -137,7 +137,8 @@ namespace ImageSharp.Tests
                  "TestImages/Formats/", // Here for code coverage tests.
                   "tests/ImageSharp.Tests/TestImages/Formats/", // from travis/build script
                   "../../../ImageSharp.Tests/TestImages/Formats/", // from Sandbox46
-                  "../../../../TestImages/Formats/"
+                  "../../../../TestImages/Formats/",
+                  "../../../TestImages/Formats/"
             };
 
             directories = directories.SelectMany(x => new[]