(VDB-267) Remove pit file stability fee

- Method is no longer present on the Pit contract

db/migrations/1542222088_drop_pit_file_stability_fee.down.sql

@@ -0,0 +1,13 @@
+CREATE TABLE maker.pit_file_stability_fee (
+  id SERIAL PRIMARY KEY,
+  header_id INTEGER NOT NULL REFERENCES headers (id) ON DELETE CASCADE,
+  what      TEXT,
+  data      TEXT,
+  log_idx   INTEGER NOT NULL,
+  tx_idx    INTEGER NOT NULL,
+  raw_log   JSONB,
+  UNIQUE (header_id, tx_idx, log_idx)
+);
+
+ALTER TABLE public.checked_headers
+  ADD COLUMN pit_file_stability_fee_checked BOOLEAN NOT NULL DEFAULT FALSE;

db/migrations/1542222088_drop_pit_file_stability_fee.up.sql

@@ -0,0 +1,4 @@
+DROP TABLE maker.pit_file_stability_fee;
+
+ALTER TABLE public.checked_headers
+  DROP COLUMN pit_file_stability_fee_checked;