test(cypress): only run in parallel for pull requests

[max-nextcloud]

Results from pushes to integration branches are usually not time critical.
Save some resources by avoiding the overhead of parallelization.

https://github.com/nextcloud/text/actions/runs/6089520881 is how pushes to integration branches would look in the future.

[cypress]

3 failed and 3 flaky tests on run #12036 ↗︎

3

141

18

0

3

Details:

test(cypress): only run in parallel for pull requests
Project: Text	Commit: f30ba20ecd
Status: Failed	Duration: 06:56 💡
Started: Sep 6, 2023 6:12 AM	Ended: Sep 6, 2023 6:19 AM

  cypress/e2e/attachments.spec.js • 3 failed tests

View Output Video

Test		Artifacts
Test all attachment insertion methods > test if attachment folder is moved with the markdown file		Output Screenshots
Test all attachment insertion methods > test if attachment folder is copied when copying a markdown file		Output Screenshots
Test all attachment insertion methods > [share] check everything behaves correctly on the share target user side		Output Screenshots

  share.spec.js • 1 flaky test

View Output Video

Test		Artifacts
Open test.md in viewer > Share a file with download disabled shows an error		Output Screenshots

  api/SessionApi.spec.js • 1 flaky test

View Output Video

Test		Artifacts
The session Api > open the session > returns connection		Output Screenshots

  api/SyncServiceProvider.spec.js • 1 flaky test

View Output Video

Test		Artifacts
Sync service provider > recovers from a dropped message		Output Screenshots

_{This comment has been generated by cypress-bot as a result of this project's GitHub integration settings.}

[skjnldsv]

I'm not sure it will save us that much time, but 👍