Fixed content dicts to be valid OpenAPI

For functions that return JPEGs, we were
 using "content_type": "image/jpeg"
 instead we should use "content": { "image/jpeg": {}}

openflexure_microscope/api/v2/views/actions/camera.py

@@ -71,7 +71,7 @@ class RAMCaptureAPI(ActionView):
     args = BasicCaptureArgs()
     responses = {
         200: {
-            "content_type": "image/jpeg",
+            "content": { "image/jpeg": {} },
             "description": "A JPEG image, representing the capture"
         }
     }