Upgrade priority: Medium (timely upgrade recommended) - due to change(s): Fix tx-pool returning the same transaction multiple times (paritytech/substrate#6535)
 
Specs of the runtime can be found here: https://github.com/paritytech/polkadot/releases

 Schedule a majority-carries referendum to be tabled next once it is legal to schedule
 an external referendum.

 The dispatch of this call must be `ExternalMajorityOrigin`.

 - `proposal_hash`: The preimage hash of the proposal.

 Unlike `external_propose`, blacklisting has no effect on this and it may replace a
 pre-scheduled `external_propose` call.

 # <weight>
 - Complexity: `O(1)`
 - Db write: `NextExternal`
 - Base Weight: 3.065 µs
 # </weight>

- There is a problem with the tx-pool returning the same transaction multiple times.
- It is recommended to upgrade the software to fix this problem.
- The upgrade is considered medium priority and should be done in a timely manner.
- More information about the upgrade can be found at the provided link.
- The upgrade will improve the performance of the software.

#171 Kusama runtime upgrade