Fix turn data mode parameter and enum member name

[stefankiesz]

What was changed?

• The TURN_CONNECTION_DATA_TRANSFER_MODE parameter passed into the createTurnConnection call in iceAgentInitRelayCandidate.
• The name of one of the members of the TURN_CONNECTION_DATA_TRANSFER_MODE enum.

Why was it changed?

• The passed parameter was changed because not only is it not used, the enum value that parameter is to set gets hardcoded in the same function to be a different enum value from the one passed in making it very confusing.
• The enum member name had a typo.

How was it changed?

• The passed parameter was changed to NULL.
• The typo was corrected.

What testing was done for the changes?

• Allowing for the CI tests to pass.

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