[FLINK-27437][tests-tpcds] Syntax error when running tpcds test

[paul8263]

What is the purpose of the change

Fix syntax error when running tpc-ds test. Only bash support process substitution while running bash via sh does not.

Brief change log

• flink-end-to-end-tests/flink-tpcds-test/README.md

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[flinkbot]

CI report:

• 0ba7194 Azure: SUCCESS

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