tests: Upgrade to Jest 26 (#28113)

client/shared/dev/jest-environment.js

@@ -12,7 +12,7 @@
  */
 const { TextEncoder } = require('util')
 
-const { JestFakeTimers } = require('@jest/fake-timers')
+const { ModernFakeTimers } = require('@jest/fake-timers')
 const { Crypto } = require('@peculiar/webcrypto')
 const { ModuleMocker } = require('jest-mock')
 const { installCommonGlobals } = require('jest-util')
@@ -81,7 +81,7 @@ class JSDOMEnvironment {
       idToRef: id => id,
       refToId: reference => reference,
     }
-    this.fakeTimers = new JestFakeTimers({
+    this.fakeTimers = new ModernFakeTimers({
       config,
       global,
       moduleMocker: this.moduleMocker,

package.json

@@ -264,7 +264,7 @@
     "html-webpack-plugin": "^5.3.2",
     "http-proxy-middleware": "^1.1.2",
     "identity-obj-proxy": "^3.0.0",
-    "jest": "^25.5.4",
+    "jest": "^26.6.3",
     "jest-canvas-mock": "^2.3.0",
     "jest-mock-extended": "^2.0.2-beta2",
     "jsdom": "^15.2.1",