fix(ble): Increase max size of the firmware string

For some development builds, the firmware version string can get quite
long.  For example: `v1.17-123-g2120027c-dirty`.  To ensure such
long versions still get transmitted properly, increase the buffer size
to 32 bytes.  Let's hope that's enough for now...
2 jobs for !505 with rahix/longer-ble-version in 56 seconds (queued for 7 seconds)
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