[in_app_purchase] Remove skipped driver test

[mklim]

Description

This test was never providing much value since it needed to be run
manually and only verified one of the API calls. Manually opening the
configured example app took just as much time and verified much more. CI
is failing based on it being skipped right now. Remove it completely to
unbreak CI.

Related Issues

flutter/flutter#29462
https://cirrus-ci.com/task/5776347504312320

Checklist

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• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (flutter analyze) does not report any problems on my PR.
• I read and followed the Flutter Style Guide.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy.
• I updated CHANGELOG.md to add a description of the change.
• I signed the CLA.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
• No, this is not a breaking change.

/cc @BugsBunnyBR

[cyanglaz]

LGTM! Remember to update version and CHANGELOG before commit

[mklim]

LGTM! Remember to update version and CHANGELOG before commit

I wasn't planning on publishing the changes here on their own since they're just removing a normally unused test within the plugin itself. Do you think it's worth pushing?

[collinjackson]

Personally I'm in favor of releasing whenever anything changes, patch changes don't really create work for anyone and it avoids a situation where someone could be confused by differences between pub and GitHub.

[mklim]

Makes sense, updated.