AP_Logger: Write_VER keep g++ 7.5 happy by removeing non-trivial designated initializers

[IamPete1]

Same problem as #25362:

../../libraries/AP_Logger/AP_Logger_Backend.cpp: In member function ‘bool AP_Logger_Backend::Write_VER()’:
../../libraries/AP_Logger/AP_Logger_Backend.cpp:579:5: sorry, unimplemented: non-trivial designated initializers not supported
     };
     ^

This keeps g++ 7.5 working for now, at some point I guess we might want say we don't support it anymore.

[khancyr]

I think we already don't support it as we need gcc10 to make the firmware fit into the small boards

[peterbarker]

As @khancyr points out, we require >= 10.2 on our ChibiOS boards.

... I think the question is, "what's the default compiler on Ubuntu 20.04?"

We no longer need to support Ubuntu 18.04, so if the default on Ubuntu 20.04 supports the existing syntax I suggest we add a block similar to https://github.com/ardupilot/ardupilot/blob/master/Tools/ardupilotwaf/boards.py#L1154 into class Linux, class SITL and class ESP32....

[peterbarker]

... if we decide instead to accept this PR, let's put a comment in place or this is going to keep happening :-)