fix(scheduler-targetes-alpha): multiple schedules cause resolution error during synth

[Tietew]

Reason for this change

Creating multiple Schedules causes Resolution Error during synth.
This PR does not fix the root cause (discussing at #28713), but apply a workaround to prevent the error.

Description of changes

Use ServicePrincipal with conditions directly, instead of PrincipalWithConditions.

Description of how you validated changes

Added a feature flag {"@aws-cdk/aws-iam:minimizePolicies":true} to unit tests.
Resolution errors occur before fix. No errors occur after fix.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

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AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: f98781c
• Result: SUCCEEDED
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[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[aahung]

@Tietew @xazhao 🚀 👏

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