tiny doc polish

libvips/draw/draw.c

@@ -69,7 +69,7 @@
  * to be a slow way to do it. This is where the draw operations come in.
  *
  * To use these operations, use vips_copy() to make a copy of the image you 
- * want to modify, to ensure that no one else is using it, then call a 
+ * want to modify to ensure that no one else is using it, then call a 
  * series of draw operations.
  * Once you are done drawing, return to normal use of vips operations. Any time
  * you want to start drawing again, you'll need to copy again.