Use back mobile_scanner pub.dev release

[monsieurtanuki]

There was a bug in mobile_scanner about zoom management (3.2.0) (cf. #4133 #3935). This bug was fixed, but no new version was uploaded to pub.dev.
We had to use our own branch in order to get that bug fix (cf. ml_kit's pubspec.yaml):

mobile_scanner:
    git:
      url: https://github.com/openfoodfacts/mobile_scanner.git
      ref: 5aa2c11915467b19dfc5fd3a9e59641d2958ffeb

Now there's a new version of mobile_scanner: 3.3.0.
We should probably use now that version instead of maintaining a custom version. Assuming that the initial bug is indeed fixed in 3.3.0.