Updated - select 3D model for SIM800C

Added 3D model for GSM modem SIM800C Link to Pull Request for adding 3D model: https://github.com/KiCad/kicad-packages3D/pull/568

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All contributions to the kicad library must follow the KiCad library convention

Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• Provide a URL to a datasheet for the footprint(s) you are contributing (without changes)
• An example screenshot image is very helpful
• If there are matching symbol or 3D model pull requests, provide link(s) as appropriate
• Check the output of the Travis automated check scripts - fix any errors as required
• Give a reason behind any intentional library convention rule violation.