Apply suggestions from code review

Co-authored-by: Sebastian Ehlert <28669218+awvwgk@users.noreply.github.com>

Author: jvdp1

src/stdlib_logger.f90

@@ -1103,8 +1103,6 @@ subroutine log_message( self, message, module, procedure, prefix )
             end if
         end if
 
-        deallocate( buffer )
-        len_buffer = 0
 
         return
 
@@ -1203,7 +1201,6 @@ subroutine log_text_error( self, line, column, summary, filename,  &
                 write( self % log_units(lun), '(a)' ) buffer
             end do
         end if
-        deallocate( buffer )
 
     contains