Bump: 0.12.0-next -> 0.13.0

[fisuda]

Proposed changes

This PR bumps NGSI Go version from 0.12.0-next -> 0.13.0.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Update only documentation, not any source code.

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• I have read the CONTRIBUTING doc
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Further comments

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[coveralls]

coverage: 100.0%. remained the same when pulling d328e1a on fisuda:release_0.13.0 into f3574b3 on lets-fiware:main.