fix(fms): use station declination for pbx/pbd

[BlueberryKing]

Fixes #9095

Summary of Changes

Uses station declination as magvar instead of database for PBX/PBD waypoints. This has been fixed before but regressed in fms-v2.

Screenshots (if necessary)

Before (KSFO Quiet Bridge Visual)

After

References

Additional context

Discord username (if different from GitHub):

Testing instructions

Use testing instructions of original PR https://github.com/flybywiresim/aircraft/pull/8182

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