<!-- Please describe your changes on the following line: -->
Remove unused `FrameChange::document_ready` field and remove unused boolean in `ConstellationMsg::GetPipeline`'s second argument.
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<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#14693
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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because compiler validates the field is not used anywhere
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Source-Repo: https://github.com/servo/servo
Source-Revision: 61d8f4d6883a876fae81bede4dfedacc764ba2f2
a34e981c7e