Avoid non-ASCII character in public header file.
diff --git a/include/freetype/ftimage.h b/include/freetype/ftimage.h
index 4b5e3b4..4199bb7 100644
--- a/include/freetype/ftimage.h
+++ b/include/freetype/ftimage.h
@@ -855,7 +855,7 @@
* The coverage value is always between 0 and 255. If you want less gray
* values, the callback function has to reduce them by scaling the
* outline four times and using bilevel monochrome renderer to then
- * average 16 pixels in each 4×4 box.
+ * average 16~pixels in each 4-by-4 box.
*
* The only correct way to blend colors is to convert the colors from
* sRGB to linear colorspace, then perform the weighted average, then
