Update intervention/image package

Also fix a unit test, the image package had changed how it loads images
so my test for is a file upload an image was failing

app/Http/Controllers/MicropubMediaController.php

@@ -149,7 +149,7 @@ class MicropubMediaController extends Controller
         try {
             $image = $manager->read($request->file('file'));
             $width = $image->width();
-        } catch (DecoderException) {
+        } catch (Exception) {
             // not an image
             $width = null;
         }