Remove performance metrics from cypress (#9467)

They are unfortunately unreliable and have been broken since June anyways.

cypress/plugins/index.ts

@@ -18,7 +18,6 @@ limitations under the License.
 
 import PluginEvents = Cypress.PluginEvents;
 import PluginConfigOptions = Cypress.PluginConfigOptions;
-import { performance } from "./performance";
 import { synapseDocker } from "./synapsedocker";
 import { slidingSyncProxyDocker } from "./sliding-sync";
 import { webserver } from "./webserver";
@@ -30,7 +29,6 @@ import { log } from "./log";
  */
 export default function(on: PluginEvents, config: PluginConfigOptions) {
     docker(on, config);
-    performance(on, config);
     synapseDocker(on, config);
     slidingSyncProxyDocker(on, config);
     webserver(on, config);

cypress/plugins/performance.ts

@@ -1,47 +0,0 @@
-/*
-Copyright 2022 The Matrix.org Foundation C.I.C.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-/// <reference types="cypress" />
-
-import * as path from "path";
-import * as fse from "fs-extra";
-
-import PluginEvents = Cypress.PluginEvents;
-import PluginConfigOptions = Cypress.PluginConfigOptions;
-
-// This holds all the performance measurements throughout the run
-let bufferedMeasurements: PerformanceEntry[] = [];
-
-function addMeasurements(measurements: PerformanceEntry[]): void {
-    bufferedMeasurements = bufferedMeasurements.concat(measurements);
-    return null;
-}
-
-async function writeMeasurementsFile() {
-    try {
-        const measurementsPath = path.join("cypress", "performance", "measurements.json");
-        await fse.outputJSON(measurementsPath, bufferedMeasurements, {
-            spaces: 4,
-        });
-    } finally {
-        bufferedMeasurements = [];
-    }
-}
-
-export function performance(on: PluginEvents, config: PluginConfigOptions) {
-    on("task", { addMeasurements });
-    on("after:run", writeMeasurementsFile);
-}