Bug 1731321 [wpt PR 30781] - [Re-Factor Client Hints] (5) Remove (unlaunched) `lang...

Bug 1731321 [wpt PR 30781] - [Re-Factor Client Hints] (5) Remove (unlaunched) `lang` client hint, a=testonly

Automatic update from web-platform-tests
[Re-Factor Client Hints] (5) Remove (unlaunched) `lang` client hint (#30781)

Now that we've cleaned up the array indexing that was blocking this,
let's move forward with removing this unused client hint.

This is a part of a series of CLs to re-factor the client hints code:
(1) Label hints with legacy names
(2) Fix the naming of (unlaunched) `lang` client hint
(3) Consolidate client hint name lists
(4) Migrate from array to map indexing for client hint names
(5) Remove (unlaunched) `lang` client hint

Bug: 1227043
Change-Id: I57404516cd1f39f738f0fbd7c202de7adf063d98
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3160286
Auto-Submit: Ari Chivukula <arichiv@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: David Dorwin <ddorwin@chromium.org>
Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/main@{#921893}

Co-authored-by: Ari Chivukula <arichiv@chromium.org>
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wpt-commits: 1691e2c6a184e2eff0a5c29b22b82aaa01840f9f
wpt-pr: 30781