Auto merge of #9440 - ehuss:fix-metrics-test, r=Eh2406
Auto merge of #9440 - ehuss:fix-metrics-test, r=Eh2406

Fix problem with metrics test.

The `counter_zero_slot` test was checking for an assertion that only fires in a debug build. However, upstream `rust-lang/rust` runs tests in `--release` mode. This unblocks the upstream update.

eminence/cargo,eminence/cargo,eminence/cargo,nipunn1313/cargo,rust-lang/cargo,rustyhorde/cargo,rust-lang/cargo,eminence/cargo,nipunn1313/cargo,rustyhorde/cargo,rustyhorde/cargo,nipunn1313/cargo,nipunn1313/cargo,rust-lang/cargo,rustyhorde/cargo,rust-lang/cargo