refactor: #be drop legacy migrations

backend/migrations/20220223103712_prototype.js

-/**
- * @param { import("knex").Knex } knex
- * @returns { Promise<void> }
- */
-exports.up = function (knex) {
-  return knex.schema
-    .createTable("images", function (table) {
-      table.increments("id").primary();
-      table.string("filename", 200);
-      table.string("md5", 255);
-      table.binary("image");
-    })
-    .createTable("game_results", function (table) {
-      table.increments("id").primary();
-      table.string("transcription", 255);
-      table.integer("gametime", 11).notNullable();
-      table.integer("id_image", 11).notNullable();
-      table.foreign("id_image").references("id").inTable("images");
-    });
-};
-
-/**
- * @param { import("knex").Knex } knex
- * @returns { Promise<void> }
- */
-exports.down = function (knex) {
-  return knex.schema.dropTable("game_results").dropTable("images");
-};

backend/migrations/20220404140016_drop_prototype.ts

-import { Knex } from "knex";
-
-export async function up(knex: Knex): Promise<void> {
-  return knex.schema.dropTable("game_results").dropTable("images");
-}
-
-export async function down(knex: Knex): Promise<void> {
-  // NOTE: we're not interested in reversing this.
-}