lib: Reword "use the functions below" docs

Those usually appear in struct definitions which will be at the bottom
of the docs, so there's nothing but the bottom of the page below.

libfprint/fprint.h

@@ -42,7 +42,7 @@ extern "C" {
  * fp_dscv_dev:
  *
  * #fp_dscv_dev is an opaque structure type.  You must access it using the
- * functions below.
+ * functions in this section.
  */
 struct fp_dscv_dev;
 
@@ -50,7 +50,7 @@ struct fp_dscv_dev;
  * fp_dscv_print:
  *
  * #fp_dscv_print is an opaque structure type.  You must access it using the
- * functions below.
+ * functions in this section.
  */
 struct fp_dscv_print;
 
@@ -58,7 +58,7 @@ struct fp_dscv_print;
  * fp_dev:
  *
  * #fp_dev is an opaque structure type.  You must access it using the
- * functions below.
+ * functions in this section.
  */
 struct fp_dev;
 
@@ -66,7 +66,7 @@ struct fp_dev;
  * fp_driver:
  *
  * #fp_driver is an opaque structure type.  You must access it using the
- * functions below.
+ * functions in this section.
  */
 struct fp_driver;
 
@@ -74,7 +74,7 @@ struct fp_driver;
  * fp_print_data:
  *
  * #fp_print_data is an opaque structure type.  You must access it using the
- * functions below.
+ * functions in this section.
  */
 struct fp_print_data;
 
@@ -82,7 +82,7 @@ struct fp_print_data;
  * fp_img:
  *
  * #fp_img is an opaque structure type.  You must access it using the
- * functions below.
+ * functions in this section.
  */
 struct fp_img;
 
@@ -293,7 +293,7 @@ uint32_t fp_print_data_get_devtype(struct fp_print_data *data);
  * fp_minutia:
  *
  * #fp_minutia is an opaque structure type.  You must access it using the
- * functions below.
+ * functions in this section.
  */
 struct fp_minutia;