Recording canvas fp. script paths does not clean up existing DNR_FP_SCRIPT_* rules #3189

Existing rules should get removed instead. For example:

1. Enable local learning
2. Inspect PB's background process and get existing DNR_FP_SCRIPT_* (BLOCK/SURROGATE_REDIRECT) DNR rules for jsdelivr.net:

(await chrome.declarativeNetRequest.getDynamicRules()).filter(r => r.condition.requestDomains &&
  r.condition.requestDomains[0].endsWith("jsdelivr.net") && [65, 66].includes(r.priority))

3. Visit https://efforg.github.io/privacybadger-test-fixtures/html/fingerprinting.html
4. Get the rules again

If you got 15 rules the first time, the second time returns 31 rules (15 + 15 + 1 new path block rule).

When this bug is fixed, the second time should return 16 (15 + 1) rules.

Will probably want to clean up existing DNR_FP_SCRIPT_* rules as part of fpStoreUpdateQueue handling in src/lib/dnr/subscribers.js, similarly to how we clean up existing DNR_SURROGATE_REDIRECT / DNR_USER_SURROGATE_REDIRECT rules as part of rebuilding surrogated resource redirect rules.