doc: remove warning about IAM beta

[fehrnah]

Description

IAM resources had a warning about a private bets.
The IAM is now in open beta and available to everyone, so the warning is not needed anymore

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (improve existing resource(s) or datasource(s))
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings or issues
• I have added acceptance tests that prove my fix is effective or that my feature works
• New and existing acceptance tests pass locally with my changes
• I ran succesfully go mod vendor if I added or modify go.mod file

[ovh-cds]

CDS Report terraform-provider-ovh-check#1863.0 ✔
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[ovh-cds]

CDS Report terraform-provider-ovh-testacc#1863.0 ■

[ovh-cds]

CDS Report terraform-provider-ovh-testacc#1863.0 ■

[ovh-cds]

CDS Report terraform-provider-ovh-check#1864.0 ✔
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• checks ✔

[ovh-cds]

CDS Report terraform-provider-ovh-testacc#1864.0 ■
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• checks ■

[ovh-cds]

CDS Report terraform-provider-ovh-testacc#1864.0 ■
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[Stoakes]

Hello,

Anyone available to merge this one ?

[scraly]

Thanks :)