fix: jpeg signature tests

Author: gregnr

src/lib/still-camera.test.ts

@@ -5,5 +5,5 @@ test('takeImage() returns JPEG', async () => {
 
   const jpegImage = await stillCamera.takeImage();
 
-  expect(jpegImage.indexOf(await StillCamera.getJpegSignature())).toBe(0);
+  expect(jpegImage.indexOf(StillCamera.jpegSignature)).toBe(0);
 });

src/lib/stream-camera.test.ts

@@ -11,7 +11,7 @@ test('Method takeImage() grabs JPEG from MJPEG stream', async () => {
 
   await streamCamera.stopCapture();
 
-  expect(jpegImage.indexOf(await StreamCamera.getJpegSignature())).toBe(0);
+  expect(jpegImage.indexOf(StreamCamera.jpegSignature)).toBe(0);
 });
 
 test('Method createStream() returns a stream of video data', async () => {