Update doc

lib/includes/nghttp2/nghttp2.h

@@ -4096,7 +4096,7 @@ nghttp2_session_check_server_session(nghttp2_session *session);
  * that value as window_size_increment is queued.  If the
  * |window_size_increment| is larger than the received bytes from the
  * remote endpoint, the local window size is increased by that
- * difference.  If the sole intention is to increase the local window
+ * difference.  If the sole purpose is to increase the local window
  * size, consider to use `nghttp2_session_set_local_window_size()`.
  *
  * If the |window_size_increment| is negative, the local window size
@@ -4105,8 +4105,8 @@ nghttp2_session_check_server_session(nghttp2_session *session);
  * (`nghttp2_option_set_no_auto_window_update()`), and the library
  * decided that the WINDOW_UPDATE should be submitted, then
  * WINDOW_UPDATE is queued with the current received bytes count.  If
- * the sole intention is to decrease the local window size, consider
- * to use `nghttp2_session_set_local_window_size()`.
+ * the sole purpose is to decrease the local window size, consider to
+ * use `nghttp2_session_set_local_window_size()`.
  *
  * If the |window_size_increment| is 0, the function does nothing and
  * returns 0.