Fix indendation

[Monceber]

• misleading indendation (implying lines are part of the if-statement while they are not) has been removed
  This was causing following warning:

/verovio/cmake/../include/zip/zip_file.hpp:1985:5: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
 1985 |     if (d->m_pOutput_buf < d->m_pOutput_buf_end) \
      |     ^~