chore(bidi): don't set Accept-Language header for a locale override

[hbenl]

Follow-up to #38079: The spec is being updated so that browsers should automatically change the Accept-Language header when a locale override is set. This is now implemented in both Chrome and Firefox, so let's remove the workaround I initially added.

[github-actions]

Test results for "MCP"

2 flaky

⚠️ [chrome] › mcp/cdp.spec.ts:24 › cdp server `@mcp-windows-latest`
⚠️ [chrome] › mcp/cdp.spec.ts:35 › cdp server reuse tab `@mcp-windows-latest`

2638 passed, 116 skipped

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Merge workflow run.

[github-actions]

Test results for "tests 1"

3 flaky

⚠️ [firefox-library] › library/inspector/cli-codegen-1.spec.ts:1079 › cli codegen › should not throw csp directive violation errors `@firefox-ubuntu-22.04-node18`
⚠️ [firefox-page] › page/page-event-request.spec.ts:182 › should return response body when Cross-Origin-Opener-Policy is set `@firefox-ubuntu-22.04-node18`
⚠️ [installation tests] › validate-dependencies.spec.ts:67 › should not validate dependencies on launch if validated during install `@package-installations-ubuntu-latest`

40250 passed, 787 skipped

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Merge workflow run.