Evas textblock: make an if look nicer (no logic change).

This makes things simpler and less confusing and might have prevented
the issue Stefan fixed in 4f484b81d4
from happenning in the first place.

src/lib/evas/canvas/evas_object_textblock.c

@@ -5817,7 +5817,7 @@ _escaped_char_get(const char *s, const char *s_end)
           }
 
         len = s_end - s;
-        if (len >= sizeof(ustr) + 1)
+        if (len > sizeof(ustr))
            len = sizeof(ustr);
 
         memcpy(ustr, s, len);