Update dependency webview_flutter to v4

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
webview_flutter	dependencies	major	^3.0.0 -> ^4.0.0

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Release Notes

flutter/plugins

v4.0.1

Compare Source

• Exposes WebResourceErrorType from platform interface.

v4.0.0

Compare Source

• BREAKING CHANGE Updates implementation to use the 2.0.0 release of
  webview_flutter_platform_interface. See Usage section in the README for updated usage. See
  Migrating from 3.0 to 4.0 section in the README for details on migrating to this version.
• Updates minimum Flutter version to 3.0.0.
• Updates code for new analysis options.
• Updates references to the obsolete master branch.

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Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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• If you want to rebase/retry this PR, check this box

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This PR has been generated by Mend Renovate. View repository job log here.

[renovate]

⚠ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: pubspec.lock

Command failed: docker run --rm --name=renovate_sidecar --label=renovate_child -v "/mnt/renovate/gh/robertodoering/harpy":"/mnt/renovate/gh/robertodoering/harpy" -v "/tmp/renovate-cache":"/tmp/renovate-cache" -v "/tmp/containerbase":"/tmp/containerbase" -e BUILDPACK_CACHE_DIR -e CONTAINERBASE_CACHE_DIR -w "/mnt/renovate/gh/robertodoering/harpy" docker.io/renovate/sidecar bash -l -c "install-tool flutter 3.3.10 && flutter pub upgrade"
Because harpy depends on twitter_webview_auth ^0.1.1 which depends on webview_flutter ^3.0.0, webview_flutter ^3.0.0 is required.
So, because harpy depends on webview_flutter ^4.0.0, version solving failed.
pub finished with exit code 1