Fix env variable loading in Cost Benchmark workflow #30866

Job	Run time
Check environment variables	10s
Build python source distribution	51s
Build python cp39- wheels on auto for ubuntu-20.04	23m 16s
Prepare GCS	0s
Build python cp310- wheels on auto for ubuntu-20.04	32m 12s
Build python cp311- wheels on auto for ubuntu-20.04	24m 22s
Build python cp312- wheels on auto for ubuntu-20.04	27m 25s
Build python cp39- wheels on auto for macos-13	23s
Build python cp310- wheels on auto for macos-13	16s
Build python cp311- wheels on auto for macos-13	30s
Build python cp312- wheels on auto for macos-13	5m 4s
Build python cp39- wheels on auto for windows-latest	16s
Build python cp310- wheels on auto for windows-latest	23s
Build python cp311- wheels on auto for windows-latest	12s
Build python cp312- wheels on auto for windows-latest	5m 17s
Build python cp39- wheels on aarch64 for ubuntu-20.04	33s
Upload python source distribution to GCS bucket	0s
Build python cp310- wheels on aarch64 for ubuntu-20.04	35s
Build python cp311- wheels on aarch64 for ubuntu-20.04	34s
Build python cp312- wheels on aarch64 for ubuntu-20.04	56m 28s
Branch repo nightly	0s
Upload wheels to GCS bucket	0s
List files on Google Cloud Storage Bucket	0s
	2h 58m 47s

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