Able to keep callsign as an i1, after switching from OfC+

[XtraFry]

Describe the bug
A clear and concise description of what the bug is.
After setting your tagline on OfC+, you can switch to anything under Union i1 and the tagline sticks which obviously you wouldnt want to avoid confusion.

To reproduce
Steps to reproduce the behaviour:

1. Flag up as OfC.
2. Set Tagline
3. Switch to Union i1 or lower.
4. See tagline issue.

Expected behaviour
It just needs to be locked even when you switch teams.

Screenshots
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impulse version (press F1 in the bottom right):

Lua error
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Additional context
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[sophfee]

not necessarily a bug, just never prevented callsign being assigned on ranks lower than OfC