Remove excess error from config

[Earlopain]

Seems to have been left unused since 8266572

Now this causes build failures in windows CI, not sure why only now:

src/diagnostic.c:781:46: error: array subscript 329 is above array bounds of 'const pm_diagnostic_data_t[329]' [-Werror=array-bounds=]
compiling build/shared/integer.o
  781 |     const char *message = diagnostic_messages[diag_id].message;
compiling build/shared/json.o
      |                           ~~~~~~~~~~~~~~~~~~~^~~~~~~~~
compiling build/shared/line_offset_list.o
src/diagnostic.c: In function 'pm_diagnostic_list_append':
src/diagnostic.c:97:35: note: while referencing 'diagnostic_messages'
   97 | static const pm_diagnostic_data_t diagnostic_messages[PM_DIAGNOSTIC_ID_MAX] = {
      |                                   ^~~~~~~~~~~~~~~~~~~

[Earlopain]

Hm, I thought it would be related to this, but I guess not