Fix bug where FILE is closed when passing to darr_(write|read)

src/darr.c

@@ -61,7 +61,6 @@ byte darr_at(darr_t *darr, size_t index)
 void darr_write_file(darr_t *bytes, FILE *fp)
 {
   size_t size = fwrite(bytes->data, bytes->used, 1, fp);
-  fclose(fp);
   assert(size == 1);
 }
 
@@ -73,7 +72,6 @@ darr_t darr_read_file(FILE *fp)
   darr_init(&darr, size);
   fseek(fp, 0, SEEK_SET);
   size_t read = fread(darr.data, size, 1, fp);
-  fclose(fp);
   assert(read == 1);
   return darr;
 }