bump libocpp version to 673bc5bf5db3a02d03f4f06cc2d9a575cbe53f39

[Pietfried]

Describe your changes

Update libocpp version to 673bc5bf5db3a02d03f4f06cc2d9a575cbe53f39 . This introdcues a timeout for OCPP messages initiated by the libocpp consumer and enables persisting those messages in case of a powerloss

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Checklist before requesting a review

• [x] I have performed a self-review of my code
• [ ] I have made corresponding changes to the documentation
• [x] I read the contribution documentation and made sure that my changes meet its requirements