[flake8-logging] Stabilize root-logger-call (LOG015) (#16654)

Summary
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Stabilizes LOG015. The tests and docs looked good.

Test Plan
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1 closed documentation issue from 4 days after the rule was added, but
no other issues or PRs.

Author: ntBre

crates/ruff_linter/src/codes.rs

@@ -1136,7 +1136,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Flake8Logging, "007") => (RuleGroup::Stable, rules::flake8_logging::rules::ExceptionWithoutExcInfo),
         (Flake8Logging, "009") => (RuleGroup::Stable, rules::flake8_logging::rules::UndocumentedWarn),
         (Flake8Logging, "014") => (RuleGroup::Preview, rules::flake8_logging::rules::ExcInfoOutsideExceptHandler),
-        (Flake8Logging, "015") => (RuleGroup::Preview, rules::flake8_logging::rules::RootLoggerCall),
+        (Flake8Logging, "015") => (RuleGroup::Stable, rules::flake8_logging::rules::RootLoggerCall),
 
         _ => return None,
     })