Update docs on topology description queries to reflect const-ness (#936)

Author: vector-of-bool

src/libmongoc/doc/includes/cast-away-td-const.txt

@@ -10,15 +10,14 @@ Synopsis
 
   bool
   mongoc_topology_description_has_readable_server (
-     mongoc_topology_description_t *td, const mongoc_read_prefs_t *prefs);
+    const mongoc_topology_description_t *td, const mongoc_read_prefs_t *prefs);
 
-Determines if the topology has a readable server available.
-Servers are filtered by the given read preferences only if the driver is connected to a replica set, otherwise the read preferences are ignored.
-This function uses the driver's current knowledge of the state of the MongoDB server or servers it is connected to; it does no I/O and it does not block.
+Determines if the topology has a readable server available. Servers are filtered
+by the given read preferences only if the driver is connected to a replica set,
+otherwise the read preferences are ignored. This function uses the driver's
+current knowledge of the state of the MongoDB server or servers it is connected
+to; it does no I/O and it does not block.
 
-.. |td-func| replace:: ``mongoc_topology_description_has_readable_server``
-
-.. include:: includes/cast-away-td-const.txt
 
 Parameters
 ----------

src/libmongoc/doc/mongoc_topology_description_has_readable_server.rst

@@ -12,11 +12,11 @@ Synopsis
   mongoc_topology_description_has_writable_server (
      const mongoc_topology_description_t *td);
 
-Determines if the topology has a writable server available, such as a primary, mongos, or standalone. This function uses the driver's current knowledge of the state of the MongoDB server or servers it is connected to; it does no I/O and it does not block.
+Determines if the topology has a writable server available, such as a primary,
+mongos, or standalone. This function uses the driver's current knowledge of the
+state of the MongoDB server or servers it is connected to; it does no I/O and it
+does not block.
 
-.. |td-func| replace:: ``mongoc_topology_description_has_writable_server``
-
-.. include:: includes/cast-away-td-const.txt
 
 Parameters
 ----------