LibJS: Sync additional Import Attributes spec changes

[F3n67u]

Some steps were not updated with tc39/ecma262#3057. This patch syncs the remaining changes.

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[F3n67u]

@gmta I ran test262 on both my local master branch and this branch.
Both runs show the same diff result against libjs-data:

master vs libjs-data

./per_file_result_diff.py -o ../libjs-data/test262/per-file-master.json -n master.json                                  
Duration:
     +19.86s

Summary:
    Diff Tests:
        +1 ✅   +1 💀    -2 💥️   

Diff Tests:
    test/staging/sm/String/replace-math.js    💥️ -> 💀
    test/staging/sm/regress/regress-610026.js 💥️ -> ✅

this branch vs libjs-data

./per_file_result_diff.py -o ../libjs-data/test262/per-file-master.json -n sync-more-spec-changes-import-attributes.json
Duration:
     +32.35s

Summary:
    Diff Tests:
        +1 ✅   +1 💀    -2 💥️   

Diff Tests:
    test/staging/sm/String/replace-math.js    💥️ -> 💀
    test/staging/sm/regress/regress-610026.js 💥️ -> ✅

The diffs are identical between my local master and this branch, so it seems there are no new test262 differences introduced by my changes.

However, I’m wondering why there’s still a diff between my local master run and libjs-data, since libjs-data should already reflect Ladybird’s master, and my fork’s master is fully up to date with upstream.