ESM error running tests on Node.js v25

[Recent PRs](https://github.com/elastic/elastic-transport-js/actions/runs/22531994178/job/65430908486?pr=356) that run the client tests are failing on Node.js v25 with the following error: ``` file:///home/runner/work/elastic-transport-js/elastic-transport-js/client/node_modules/yargs/yargs:3 const {applyExtends, cjsPlatformShim, Parser, Yargs, processArgv} = require('./build/index.cjs') ^ ReferenceError: require is not defined in ES module scope, you can use import instead at file:///home/runner/work/elastic-transport-js/elastic-transport-js/client/node_modules/yargs/yargs:3:69 at ModuleJobSync.runSync (node:internal/modules/esm/module_job:534:37) at ModuleLoader.importSyncForRequire (node:internal/modules/esm/loader:366:47) at loadESMFromCJS (node:internal/modules/cjs/loader:1628:24) at Module._compile (node:internal/modules/cjs/loader:1793:5) at Object..js (node:internal/modules/cjs/loader:1951:10) at Module.load (node:internal/modules/cjs/loader:1532:32) at Module._load (node:internal/modules/cjs/loader:1334:12) at wrapModuleLoad (node:internal/modules/cjs/loader:255:19) at Module.require (node:internal/modules/cjs/loader:1555:12) ``` Presumably an ESM-related issue with a dev dependency that needs to get cleaned up.