Replace python with python3 in incremental_load.sh.tpl

[jbgosselin]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

On MacOS 12.3, Apple removed the default python executable.
Building images doesn't work and throw this error:
env: python: No such file or directory

Issue Number: #2046 2046

What is the new behavior?

Build on a system without python executable (as MacOS 12.3+) works as expected.

Does this PR introduce a breaking change?

• Yes
• No

Other information

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For more information, open the CLA check for this pull request.

[linzhp]

Can you sign CLA?

[jbgosselin]

I think I did sign it @linzhp