test: Fix for extractMetadataStructured test

[arjankowski]

No description provided.

[arjankowski]

This change adapting to the fix that was originally reported internally here

In general, all metadata fields are stored in the RFC 3339 format with millisecond precision, as stated in this document.

As a result, the previous assumption that the returned date was limited to the format YYYY-MM-DD was incorrect.
This fix adjusts the test to the changes introduced on the backend side.

[coveralls]

Pull Request Test Coverage Report for Build #4186

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 71.773%

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Totals
Change from base Build #4176:	0.0%
Covered Lines:	8073
Relevant Lines:	11248

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build #4183

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.003%) to 71.77%

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Files with Coverage Reduction	New Missed Lines	%
src/main/java/com/box/sdk/RealtimeServerConnection.java	1	77.78%

Totals
Change from base Build #4176:	-0.003%
Covered Lines:	8067
Relevant Lines:	11240

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💛 - Coveralls