AP_CANManager: Fix some typos

Fixed some typos found in the code.

libraries/AP_CANManager/AP_CANManager.cpp

@@ -442,7 +442,7 @@ void AP_CANManager::handle_can_frame(const mavlink_message_t &msg)
             buffer_size /= 2;
         }
         if (frame_buffer == nullptr) {
-            // disard the frames
+            // discard the frames
             return;
         }
     }

libraries/AP_CANManager/AP_CANSensor.cpp

@@ -13,7 +13,7 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 /*
-  generic CAN sensor class, for easy creation of CAN sensors using prioprietary protocols
+  generic CAN sensor class, for easy creation of CAN sensors using proprietary protocols
  */
 #include <AP_HAL/AP_HAL.h>
 

libraries/AP_CANManager/AP_SLCANIface.cpp

@@ -715,7 +715,7 @@ int16_t SLCAN::CANIface::receive(AP_HAL::CANFrame& out_frame, uint64_t& rx_time,
         }
     }
 
-    // We found nothing in HAL's CANIface recieve, so look in SLCANIface
+    // We found nothing in HAL's CANIface receive, so look in SLCANIface
     if (_port == nullptr) {
         return 0;
     }