Fix compilation error when printing Error with defmt

[Tosainu]

This fixes compilation errors like below:

error[E0277]: the trait bound `nom::internal::Err<nom::error::Error<&str>>: Format` is not satisfied
   --> nyan.rs:245:21
    |
245 |                     defmt::warn!("{:a}: {}", line, err);
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Format` is not implemented for `nom::internal::Err<nom::error::Error<&str>>`
    |
    = help: the following other types implement trait `Format`:
              &T
              &mut T
              ()
              (T0, T1)
              (T0, T1, T2)
              (T0, T1, T2, T3)
              (T0, T1, T2, T3, T4)
              (T0, T1, T2, T3, T4, T5)
            and 234 others
    = note: required for `nmea::Error<'_>` to implement `Format`
note: required by a bound in `defmt::export::fmt`

The position of adding the #[defmt()] attribute seems to be wrong according to the document. So I moved this inside the ParsingError( ... ) and I verified it now compiles and works.

[elpiel]

Good catch!
Will merge once CI passes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.67%. Comparing base (68a44c0) to head (8daf104).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #146   +/-   ##
=======================================
  Coverage   78.67%   78.67%           
=======================================
  Files          39       39           
  Lines        1449     1449           
=======================================
  Hits         1140     1140           
  Misses        309      309           

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