fix: exclude Azure Monitor scaler from metricName deprecation

[lsolovey]

Exclude Azure Monitor scaler from metricName deprecation.
metricName in AzureMonitor scaler refers to the actual name of the underlying metric in Azure.

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• When introducing a new scaler, I agree with the scaling governance policy
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Relates to kedacore/keda-docs#1152
Relates to kedacore/keda-docs#1158

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[JorTurFer]

LGTM! Nice catch