Fix CI: Remove bytes keys from tests

[jacobtomlinson]

Support for using bytes as keys was removed in dask/dask#11757. This PR removes some test cases that uses them.

Closes #9016

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

[github-actions]

Unit Test Results

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

    27 files  ± 0      27 suites  ±0   11h 43m 57s ⏱️ + 15m 36s
 4 100 tests  -  5   3 984 ✅ ±0    111 💤 ±0  5 ❌  -  4 
51 407 runs   - 66  49 103 ✅  - 2  2 297 💤 +1  7 ❌  - 64 

For more details on these failures, see this check.

Results for commit 6857899. ± Comparison against base commit cb4aa07.

This pull request removes 7 and adds 2 tests. Note that renamed tests count towards both.

distributed.http.scheduler.tests.test_scheduler_http ‑ test_call_stack_page[123]
distributed.http.scheduler.tests.test_scheduler_http ‑ test_call_stack_page[key17]
distributed.http.scheduler.tests.test_scheduler_http ‑ test_call_stack_page[key18]
distributed.http.scheduler.tests.test_scheduler_http ‑ test_task_page[123]
distributed.http.scheduler.tests.test_scheduler_http ‑ test_task_page[key17]
distributed.http.scheduler.tests.test_scheduler_http ‑ test_task_page[key18]
distributed.tests.test_client ‑ test_bytes_keys

distributed.http.scheduler.tests.test_scheduler_http ‑ test_call_stack_page[key13]
distributed.http.scheduler.tests.test_scheduler_http ‑ test_task_page[key13]

[jacobtomlinson]

Looks like CI is back to it's old self again with this change. Some flaky tests but not seeing failures across the board.

[jacobtomlinson]

I'm going to go ahead and merge this to unblock other PRs.