fix(iam): remove beta flag and add missing attribute on documentation

[Monitob]

No description provided.

[codecov-commenter]

Codecov Report

Merging #1644 (5e22ec2) into master (5292d40) will increase coverage by 4.42%.
The diff coverage is 81.98%.

❗ Current head 5e22ec2 differs from pull request most recent head 56b36f9. Consider uploading reports for the commit 56b36f9 to get more accurate results

@@            Coverage Diff             @@
##           master    #1644      +/-   ##
==========================================
+ Coverage   69.20%   73.62%   +4.42%     
==========================================
  Files         143      143              
  Lines       23095    23238     +143     
==========================================
+ Hits        15982    17109    +1127     
+ Misses       5701     4632    -1069     
- Partials     1412     1497      +85     

Impacted Files	Coverage Δ
scaleway/resource_baremetal_server.go	75.21% <73.75%> (+7.32%)	⬆️
scaleway/resource_account_project.go	83.78% <80.00%> (+83.78%)	⬆️
scaleway/provider.go	76.45% <84.61%> (+4.24%)	⬆️
scaleway/helpers_baremetal.go	81.00% <94.33%> (+5.60%)	⬆️
scaleway/helpers.go	72.85% <0.00%> (+1.75%)	⬆️
scaleway/validation.go	64.86% <0.00%> (+10.81%)	⬆️
scaleway/helpers_account.go	100.00% <0.00%> (+50.00%)	⬆️
scaleway/data_source_account_project.go	64.15% <0.00%> (+64.15%)	⬆️
scaleway/data_source_iam_ssh_key.go	65.38% <0.00%> (+65.38%)	⬆️
... and 10 more

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[kindermoumoute]

LGTM