Drop Yarn install commands in update message

Yarn users should know how to translate from npm commands already as most packages document npm commands only. It’s also unfair to other package managers, like `pnpm` and `bun` that we don’t include them and I don’t want to maintain install commands for all of them.

package.json

@@ -40,12 +40,10 @@
 		"boxen": "^7.0.0",
 		"chalk": "^5.0.1",
 		"configstore": "^6.0.0",
-		"has-yarn": "^3.0.0",
 		"import-lazy": "^4.0.0",
 		"is-ci": "^3.0.1",
 		"is-installed-globally": "^0.4.0",
 		"is-npm": "^6.0.0",
-		"is-yarn-global": "^0.4.0",
 		"latest-version": "^7.0.0",
 		"pupa": "^3.1.0",
 		"semver": "^7.3.7",

update-notifier.js

@@ -10,8 +10,6 @@ import semverDiff from 'semver-diff';
 import latestVersion from 'latest-version';
 import {isNpmOrYarn} from 'is-npm';
 import isInstalledGlobally from 'is-installed-globally';
-import isYarnGlobal from 'is-yarn-global';
-import hasYarn from 'has-yarn';
 import boxen from 'boxen';
 import {xdgConfig} from 'xdg-basedir';
 import isCi from 'is-ci';
@@ -134,20 +132,10 @@ export default class UpdateNotifier {
 
 		options = {
 			isGlobal: isInstalledGlobally,
-			isYarnGlobal: isYarnGlobal(),
 			...options,
 		};
 
-		let installCommand;
-		if (options.isYarnGlobal) {
-			installCommand = `yarn global add ${this._packageName}`;
-		} else if (options.isGlobal) {
-			installCommand = `npm i -g ${this._packageName}`;
-		} else if (hasYarn()) {
-			installCommand = `yarn add ${this._packageName}`;
-		} else {
-			installCommand = `npm i ${this._packageName}`;
-		}
+		const installCommand = options.isGlobal ? `npm i -g ${this._packageName}` : `npm i ${this._packageName}`;
 
 		const defaultTemplate = 'Update available '
 			+ chalk.dim('{currentVersion}')