fix(Proofs): Run price tag prediction only on PRICE_TAG proofs

[raphodn]

What

When diving into our usage of ML, I realized that we run the price_tag_detection model even on non-Price tag proofs.
Nevertheless, we already had a check afterwards that would avoid creating the corresponding PriceTag objects for these kinds of proofs.

So moved up the check, and will cleanup the history once it is deployed

Stats

Proof.objects.count()
// 17485

ProofPrediction.objects.count()
// 34956

ProofPrediction.objects.exclude(proof__type="PRICE_TAG").count()
// 6292

PriceTag.objects.exclude(proof__type="PRICE_TAG").count()
// 0

Counter(ProofPrediction.objects.exclude(proof__type="PRICE_TAG").values_list("model_name", flat=True))
// {'price_proof_classification': 3152, 'price_tag_detection': 3140}

[raphodn]

Ran the following command to the cleanup post-deploy

ProofPrediction.objects.exclude(proof__type="PRICE_TAG").filter(model_name="price_tag_detection").delete()
// 3143 objects deleted