ASimTester: Relax NetworkSession/EventSeverity to Recommended

[deggis]

In current ASIM common fields and NetworkSession schemas EventSeverity is listed as a Recommended field.

Change its class from Mandatory to Recommended.

https://learn.microsoft.com/en-us/azure/sentinel/normalization-common-fields https://learn.microsoft.com/en-us/azure/sentinel/normalization-schema-network

Required items, please complete

Change(s):

• ASimTester: Change EventSeverity field's class from Mandatory to Recommended

Reason for Change(s):

• To have ASIM tester function match current documentation

Version Updated:

• N/A

Testing Completed:

• N/A
• I tried modifying re-saving ASimSchemaTester with a URL to changed CSV version, but looks like the function cannot be saved using GUI.
• ASimSchemaTester has parameters "T:(ColumnName:string,ColumnType:string),selected_schema:string", and the function dialog does not support that yet.

Checked that the validations are passing and have addressed any issues that are present:

• N/A

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