Use shared runtime logs bucket

[Pigbibi]

Summary

• update the IBKR paper top50 switch doc to reference the neutral shared runtime logs bucket

Verification

• migrated gs://qsl-runtime-logs-interactivebrokersquant to gs://qsl-runtime-logs-shared
• verified object counts match: total 2486, execution reports 2141, strategy artifacts 345
• verified repository variables no longer reference the old bucket
• git diff --check