chore: remove migrated web-ide e2e tests

What does this MR do and why?

Selected Web IDE e2e tests have been migrated over to gitlab-web-ide integration tests.

This MR removes these migrated e2e tests from the test suite.

E2E Test Case	Test name	Web IDE integration test (where tests are migrated to)
add_first_file_in_web_ide_spec	'throws an error'	https://gitlab.com/gitlab-org/gitlab-web-ide/-/blob/main/tests/integration/web-ide-source-control.test.ts#L65
add_new_directory_in_web_ide_spec	'throws an error'	https://gitlab.com/gitlab-org/gitlab-web-ide/-/blob/main/tests/integration/web-ide-source-control.test.ts#L82
closing_web_ide_with_unsaved_changes_spec		https://gitlab.com/gitlab-org/gitlab-web-ide/-/blob/main/tests/integration/web-ide-source-control.test.ts#L52
upload_new_file_in_web_ide_spec	'throws an error'	https://gitlab.com/gitlab-org/gitlab-web-ide/-/blob/main/tests/integration/web-ide-source-control.test.ts#L172
upload_new_file_in_web_ide_spec	'when the file is an image'	https://gitlab.com/gitlab-org/gitlab-web-ide/-/blob/main/tests/integration/web-ide-source-control.test.ts#L159

Note: migrated tests were identified from gitlab-org/quality/quality-engineering/team-tasks#3476 (closed)

References

[Web IDE] Implement integration test for creati... (gitlab-web-ide#490 - closed)

Migrate selected Web IDE E2E tests into Playwri... (&18056 - closed)

How to set up and validate locally

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Related to #18056 (closed)