update IamAwsProvider as per minio-go implementation #529

Job	Run time
Test on python 3.8 and ubuntu-latest	2m 0s
Test on python 3.8 and windows-latest	5m 4s
Test on python 3.8 and macos-latest	46s
Test on python 3.9 and ubuntu-latest	1m 50s
Test on python 3.9 and windows-latest	4m 25s
Test on python 3.9 and macos-latest	17s
Test on python 3.10 and ubuntu-latest	1m 53s
Test on python 3.10 and windows-latest	5m 52s
Test on python 3.10 and macos-latest	13s
Test on python 3.11 and ubuntu-latest	1m 40s
Test on python 3.11 and windows-latest	5m 8s
Test on python 3.11 and macos-latest	12s
Test on python 3.12 and ubuntu-latest	1m 47s
Test on python 3.12 and windows-latest	4m 46s
Test on python 3.12 and macos-latest	11s
	36m 4s

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