Update Gateway global configuration file to contain information about all frequency plans

[ryaplots]

Summary

After the tests ran by CE on the new frequency plan ids multiselect we realized that the config file is actually not up to date with these changes.
Referencing the point 3. from https://github.com/TheThingsIndustries/lorawan-stack-support/issues/1000#issuecomment-1772764348

Steps to Reproduce

1. Create a gateway with multiple frequency plans
2. Go to the gateway overview
3. Download the global configuration file

Current Result

The Global configuration file contains information about only one frequency plan.

Expected Result

The Global configuration file to contain information about all frequency plans.

Relevant Logs

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URL

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Deployment

The Things Stack Open Source (self-hosted)

The Things Stack Version

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Client Name and Version

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Other Information

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Proposed Fix

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Contributing

• I can help by doing more research.
• I can help by implementing a fix after the proposal above is approved.
• I can help by testing the fix before it's released.

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