Rename `safe` to `expected` in `Scheduler.remove_worker`.

[hendrikmakait]

Closes #8665

• [ ] Tests added / passed
• [ ] Passes pre-commit run --all-files

[github-actions[bot]]

Unit Test Results

_See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests._

    29 files  ±    0      29 suites  ±0   11h 8m 8s :stopwatch: + 1h 18m 15s  4 059 tests  -     4   3 956 :white_check_mark: +    9     97 :zzz:  -   9  6 :x: ±0  55 911 runs  +7 605  53 742 :white_check_mark: +7 375  2 162 :zzz: +247  7 :x: ±0 

For more details on these failures, see this check.

Results for commit 7aa68225. ± Comparison against base commit 9672121c.

This pull request removes 13 and adds 9 tests. Note that renamed tests count towards both.

``` distributed.protocol.tests.test_arrow distributed.protocol.tests.test_collection distributed.protocol.tests.test_highlevelgraph distributed.protocol.tests.test_numpy distributed.protocol.tests.test_pandas distributed.shuffle.tests.test_graph distributed.shuffle.tests.test_merge distributed.shuffle.tests.test_merge_column_and_index distributed.shuffle.tests.test_metrics distributed.shuffle.tests.test_rechunk … ``` ``` distributed.diagnostics.tests.test_memray ‑ test_basic_integration_scheduler distributed.diagnostics.tests.test_memray ‑ test_basic_integration_scheduler_report_args[False] distributed.diagnostics.tests.test_memray ‑ test_basic_integration_scheduler_report_args[report_args0] distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers[1] distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers[False] distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers[True] distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers_report_args[False] distributed.diagnostics.tests.test_memray ‑ test_basic_integration_workers_report_args[report_args0] distributed.tests.test_scheduler ‑ test_remove_worker_from_scheduler_warns_on_safe ```