ArduPlane: fix Q_RTL_MODE parameter doc

ArduPlane/quadplane.cpp

@@ -187,7 +187,7 @@ const AP_Param::GroupInfo QuadPlane::var_info[] = {
 
     // @Param: RTL_MODE
     // @DisplayName: VTOL RTL mode
-    // @Description: If this is set to 1 then an RTL will change to QRTL when within RTL_RADIUS meters of the RTL destination, VTOL approach: vehicle will RTL at RTL alt and circle with a radius of Q_FW_LND_APR_RAD down to Q_RLT_ALT and then transission into the wind and QRTL, see 'AUTO VTOL Landing', QRTL Always: do a QRTL instead of RTL
+    // @Description: If this is set to 1 then an RTL will change to QRTL when within RTL_RADIUS meters of the RTL destination, VTOL approach: vehicle will RTL at RTL alt and circle with a radius of Q_FW_LND_APR_RAD down to Q_RTL_ALT and then transition into the wind and QRTL, see 'AUTO VTOL Landing', QRTL Always: do a QRTL instead of RTL
     // @Values: 0:Disabled,1:Enabled,2:VTOL approach,3:QRTL Always
     // @User: Standard
     AP_GROUPINFO("RTL_MODE", 36, QuadPlane, rtl_mode, 0),