[Espresso] remove metadata network policy

[mboetger]

It turns out the io.flutter.network-policy is not connected to the engine. Remove any mention of it. Regardless, this should control dart sockets and Espresso is only interested in Android native sockets.

Addresses: flutter/flutter#183153

Pre-Review Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] page, which explains my responsibilities.
• I read and followed the [relevant style guides] and ran [the auto-formatter].
• I signed the [CLA].
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I [linked to at least one issue that this PR fixes] in the description above.
• I followed [the version and CHANGELOG instructions], using [semantic versioning] and the [repository CHANGELOG style], or I have commented below to indicate which documented exception this PR falls under[^1].
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which [test exemption] this PR falls under[^1].
• All existing and new tests are passing.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

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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[gemini-code-assist]

Code Review

This pull request removes all references to the io.flutter.network-policy metadata tag. The documentation in README.md and the configuration in the example AndroidManifest.xml have been updated to remove it. The pubspec.yaml version is bumped to 0.4.0+23, and a corresponding entry has been added to CHANGELOG.md. My feedback focuses on improving the new changelog entry for clarity and fixing a minor formatting issue in the README.md.

[stuartmorgan-g]

LGTM. Nice sleuthing!

[auto-submit]

auto label is removed for flutter/packages/11164, Failed to merge flutter/packages/11164 with FormatException: Unexpected end of input (at character 1)

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