ignore unreachable_switch_default in weird switch case

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Breaking changes :heavy_check_mark:

| Package | Change | Current Version | New Version | Needed Version | Looking good? | | :--- | :--- | ---: | ---: | ---: | ---: | |grpc|None|4.0.2-wip|4.0.2-wip|4.0.2-wip|:heavy_check_mark:|

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| File | Coverage | | :--- | :--- | |lib/src/client/transport/web_streams.dart| :green_heart: 54 % | This check for [test coverage](https://github.com/dart-lang/ecosystem/wiki/Test-Coverage) is informational (issues shown here will not fail the PR).

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| Package | Version | Status | | :--- | ---: | :--- | | package:grpc | 4.0.2-wip | WIP (no publish necessary) | Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

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PR Health

Breaking changes :heavy_check_mark:

| Package | Change | Current Version | New Version | Needed Version | Looking good? | | :--- | :--- | ---: | ---: | ---: | ---: | |grpc|None|4.0.2-wip|4.0.2-wip|4.0.2-wip|:heavy_check_mark:|

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| Package | Changed Files | | :--- | :--- | | package:grpc | lib/src/client/transport/web_streams.dart | Changes to files need to be [accounted for](https://github.com/dart-lang/ecosystem/wiki/Changelog) in their respective changelogs. This check can be disabled by tagging the PR with `skip-changelog-check`.

Coverage :heavy_check_mark:

| File | Coverage | | :--- | :--- | |lib/src/client/transport/web_streams.dart| :green_heart: 54 % | This check for [test coverage](https://github.com/dart-lang/ecosystem/wiki/Test-Coverage) is informational (issues shown here will not fail the PR).

API leaks :warning:

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API. | Package | Leaked API symbols | | :--- | :--- | |grpc|Any
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Package publish validation :heavy_check_mark:

| Package | Version | Status | | :--- | ---: | :--- | | package:grpc | 4.0.2-wip | WIP (no publish necessary) | Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.