[two_dimensional_scrollables] Set same minimum version as rest of the repo

[bparrishMines]

Changes the minimum Dart and Flutter versions as the rest of the repo. See #4731 and https://github.com/flutter/flutter/wiki/Contributing-to-Plugins-and-Packages#version

Our CI was unable to publish this plugin with a minimum Dart version of 3.1.0 since our repo runs the publish command with version 3.0.0. See https://github.com/flutter/packages/actions/runs/5896017278/job/16010664124

Resolving dependencies...


The current Dart SDK version is 3.0.0.




Because two_dimensional_scrollables requires SDK version >=3.1.0 <4.0.0, version solving failed.


Publishing two_dimensional_scrollables failed.


The following packages had failures during publishing:
  packages/packages/two_dimensional_scrollables:
    publish failed
See above for full details.
Error: Process completed with exit code 1.

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 relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/packages repo does use dart format.)
• 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 listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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[bparrishMines]

cc @stuartmorgan FYI

[bparrishMines]

Actually it looks like this won't work:

[0:00] Running for packages/two_dimensional_scrollables...
  The minimum Dart version is 2.19.0, but the minimum Flutter version of 3.13.0 shipped with Dart 3.1.0. Please use consistent lower SDK bounds
[0:00] Running for packages/two_dimensional_scrollables/example...
  The minimum Dart version is 2.19.0, but the minimum Flutter version of 3.13.0 shipped with Dart 3.1.0. Please use consistent lower SDK bounds

[bparrishMines]

This should be fixable by this instead: #4745