fix typo

Author: cofyc

FAQs.md

@@ -32,5 +32,5 @@ Issues:
 I choose `intptr_t` because it's a integer type which also can be used to hold
 a pointer value.  Most of the time, we only need a integer to hold
 user-provided value, see `OPT_BIT` as example. If you want to provide a pointer
-which points a large amount of data, you can cast it to `intptr_t` and cast it
-back to original pointer in callback function.f
+which points to a large amount of data, you can cast it to `intptr_t` and cast
+it back to original pointer in callback function.