Add note about true cause of regression in #74468

Author: Mark-Simulacrum

triage/2020-07-21.md

@@ -28,7 +28,7 @@ Regressions
   Up to 44.8% instruction increases on many benchmarks, and 5-10% max-rss increases on many benchmarks. I have requested it be reverted.
 - [Rollup of 11 pull requests #74468](https://github.com/rust-lang/rust/pull/74468#issuecomment-661371815)
   ([instructions](https://perf.rust-lang.org/compare.html?start=d3df8512d2c2afc6d2e7d8b5b951dd7f2ad77b02&end=7d31ffc1ac9e9ea356e896e63307168a64501b9d&stat=instructions:u)):
-  Up to 10.2% losses on many benchmarks. Unclear which PR is responsible.
+  Up to 10.2% losses on many benchmarks. [#74069](https://github.com/rust-lang/rust/pull/74069) [responsible](https://perf.rust-lang.org/compare.html?start=d3df8512d2c2afc6d2e7d8b5b951dd7f2ad77b02&end=cfade73820883adf654fe34fd6b0b03a99458a51), revert [posted](https://github.com/rust-lang/rust/pull/74611).
 - [Support const args in type dependent paths (Take 2) #74113](https://github.com/rust-lang/rust/pull/74113#issuecomment-661470398)
   ([instructions](https://perf.rust-lang.org/compare.html?start=d9e8d6290745a65025a3e082aea72fbe372292c6&end=7e11379f3b4c376fbb9a6c4d44f3286ccc28d149&stat=instructions:u)):
   Up to 1.5% losses on numerous benchmarks, which was expected.