TestReader: Re-enable the lost support to read jpg/gif via convert
TestReader: Re-enable the lost support to read jpg/gif via convert

This re-enables my personal additional set of DM blackbox tests and is/should not affecting any other platform/test/user.

nu-book/zxing-cpp,huycn/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,huycn/zxing-cpp,nu-book/zxing-cpp,huycn/zxing-cpp,huycn/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,huycn/zxing-cpp,nu-book/zxing-cpp,huycn/zxing-cpp,huycn/zxing-cpp,huycn/zxing-cpp