docs: Add more removed context methods to migrate to v9 guide

[mdjermanovic]

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Adds context.getAncestors(), context.getDeclaredVariables(), context.getScope(), and context.markVariableAsUsed() to the v9 migration guide in the "Removed multiple context methods" section.

What changes did you make? (Give an overview)

Updated v9 migration guide.

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[mdjermanovic]

@christian-bromann this error happens occasionally, and usually disappears when the test is run again:

2024-01-04T09:51:01.6471352Z Execution of 1 workers started at 2024-01-04T09:51:01.644Z
2024-01-04T09:51:01.6475738Z 
2024-01-04T09:51:03.5695259Z [0-0] RUNNING in chrome - file:///tests/lib/linter/linter.js
2024-01-04T09:51:21.2183638Z [0-0]  Error:  Test failed due to following error(s):
2024-01-04T09:51:21.2187139Z   - linter.js: Failed to fetch dynamically imported module: http://localhost:46847/lib/config/flat-config-array.js: TypeError: Failed to fetch dynamically imported module: http://localhost:46847/lib/config/flat-config-array.js
2024-01-04T09:51:21.2189408Z 
2024-01-04T09:51:21.4289266Z [0-0] FAILED in chrome - file:///tests/lib/linter/linter.js
2024-01-04T09:51:21.4799836Z 
2024-01-04T09:51:21.4800947Z  "concise" Reporter:
2024-01-04T09:51:21.4807590Z ========= Your concise report ==========
2024-01-04T09:51:21.4809132Z chrome-headless-shell (v120.0.6099.109) on linux
2024-01-04T09:51:21.4812595Z ❌ Failed to setup tests, no tests found
2024-01-04T09:51:21.4814289Z 
2024-01-04T09:51:21.4815373Z 
2024-01-04T09:51:21.4820184Z Spec Files:	 0 passed, 1 failed, 1 total (100% completed) in 00:00:19 

Any ideas about what's causing it and how we could avoid it?

[christian-bromann]

Any ideas about what's causing it and how we could avoid it?

Thanks for letting me know, seems like a race condition. I will see if I find a way to improve this behavior.

[nzakas]

LGTM. Thanks!