[Port] Remove offset in default format in ConvertFromUtc pre-built function

[cosmicshuai]

closes: #5003
Now the default format of ConvertFromUtc are the same as it in WDL, which compiles "yyyy-MM-ddTHH:mm:ss.fffffffK".
See Ref:
https://docs.microsoft.com/en-us/azure/logic-apps/workflow-definition-language-functions-reference#convertFromUtc

[coveralls]

Pull Request Test Coverage Report for Build 415734109

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 84.473%

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Totals
Change from base Build 415731783:	0.003%
Covered Lines:	17640
Relevant Lines:	19955

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💛 - Coveralls