Adds setText to web engine

[chunhtai]

The previous pr forgot to add the setText to other part of the web engine. this pr fixes it

related flutter/flutter#77271

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
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  writing and running engine tests.
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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

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[chunhtai]

The test will be on the framework side, the test will pass once this engine change is in https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket.appspot.com/8853304046211326768/+/steps/run_test.dart_for_web_tests_shard_and_subshard_4/0/stdout

[justinmc]

LGTM 👍

[mdebbar]

FYI @yjbanov