fix(db): drop constraint prover_jobs_fri_l1_batch_number_fkey (#173)

# What ❔

`prover_jobs_fri_l1_batch_number_fkey` is dropped.

## Why ❔

`prover_jobs_fri` is filled only in prover DB, while `l1_batches` --
only in core DB, so we can't have the constraint.

## Checklist

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core/lib/dal/migrations/20231009073918_drop-prover_jobs_fri_l1_batch_number_fkey.down.sql

@@ -0,0 +1,2 @@
+ALTER TABLE prover_jobs_fri ADD CONSTRAINT prover_jobs_fri_l1_batch_number_fkey
+    FOREIGN KEY (l1_batch_number) REFERENCES l1_batches (number);

core/lib/dal/migrations/20231009073918_drop-prover_jobs_fri_l1_batch_number_fkey.up.sql

@@ -0,0 +1 @@
+ALTER TABLE prover_jobs_fri DROP CONSTRAINT IF EXISTS prover_jobs_fri_l1_batch_number_fkey;