Fix exponential backoff calculation #25398

Job	Run time
Classify changes	9s
Bootstrap Pants, test Rust (macOS13-x86_64)	14m 55s
Bootstrap Pants, test and lint Rust (Linux-x86_64)	20m 41s
Bootstrap Pants, test Rust (Linux-ARM64)	21m 17s
Build wheels (Linux-ARM64)	0s
Ensure PR has release notes	3s
Build wheels (Linux-x86_64)	0s
Build wheels (macOS13-x86_64)	0s
Build wheels (macOS14-ARM64)	0s
Test Python (macOS13-x86_64)	21m 19s
Test Python (Linux-x86_64) Shard 0/10	18m 5s
Test Python (Linux-x86_64) Shard 1/10	16m 57s
Test Python (Linux-x86_64) Shard 2/10	18m 45s
Test Python (Linux-x86_64) Shard 3/10	16m 3s
Lint Python and Shell	4m 34s
Test Python (Linux-x86_64) Shard 4/10	29m 31s
Test Python (Linux-x86_64) Shard 5/10	13m 36s
Test Python (Linux-x86_64) Shard 6/10	10m 31s
Test Python (Linux-x86_64) Shard 7/10	17m 3s
Test Python (Linux-x86_64) Shard 8/10	15m 37s
Test Python (Linux-x86_64) Shard 9/10	10m 58s
Test Python (Linux-ARM64)	13m 18s
Set Merge OK	0s
Merge OK	1s
	4h 23m 23s

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