docs: recommend localhost over 127.0.0.1

[Skn0tt]

Some newer dev servers don't bind to 127.0.0.1 anymore, so we shouldn't recommend it. Localhost works with most stuff. We originally recommended 127.0.0.1 for backwards compatibility with now-outdated Playwright versions: https://github.com/microsoft/playwright-blog/pull/1#discussion_r1124380341

[Copilot]

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[github-actions]

Test results for "tests 1"

1 fatal errors, not part of any test
1 failed
❌ [playwright-test] › tests/runner.spec.ts:118:5 › should ignore subprocess creation error because of SIGINT @macos-latest-node18-1

9 flaky

⚠️ [chromium-library] › tests/library/chromium/oopif.spec.ts:284:3 › should click @chromium-ubuntu-22.04-node22
⚠️ [firefox-page] › tests/page/page-evaluate.spec.ts:403:3 › should throw for too deep reference chain @firefox-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/proxy.spec.ts:93:11 › should proxy local network requests › with other bypasses › link-local @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/trace-viewer.spec.ts:247:1 › should render network bars @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/trace-viewer.spec.ts:1298:1 › should pick locator in iframe @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/video.spec.ts:411:5 › screencast › should capture css transformation @webkit-ubuntu-22.04-node18
⚠️ [webkit-page] › tests/page/page-screenshot.spec.ts:224:5 › page screenshot › should take fullPage screenshots and mask elements outside of it @webkit-ubuntu-22.04-node18
⚠️ [webkit-page] › tests/page/page-set-input-files.spec.ts:146:5 › should upload large file @webkit-ubuntu-22.04-node18
⚠️ [playwright-test] › tests/ui-mode-test-watch.spec.ts:145:5 › should watch all @windows-latest-node18-1

38035 passed, 650 skipped
✔️✔️✔️

Merge workflow run.