tests: improve consistency and clarity of test diagnostics
Minor updates to test diagnostics for consistency and readability:
- Corrected an incorrect identifier
- Standardized float formatting
No behavior changes.
Change-Id: I3d3633a7cc487209341ea92101f8c67848212080
GitHub-Last-Rev:
b2822e846a91ce2563445f90f8d5768662a9babf
GitHub-Pull-Request: golang/go#77001
Reviewed-on: https://go-review.googlesource.com/c/go/+/732762
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>