CLI: Update help message to allow rescan with remote nodes without owner key

[dbadol]

Bug description
The CLI help says that a rescan is not possible if the node does not have the owner key. However, it does not seem to be the case: a rescan IS possible.

To Reproduce
Steps to reproduce the behaviour:

1. Open the CLI wallet
2. Run beam-wallet.exe --help
3. See the information given for the rescan option.
4. Run: beam-wallet.exe rescan -n eu-nodes.mainnet.beam.mw:8100
5. After about 45 minutes the rescan will be completed!

Current behaviour
The CLI help says:
rescan the blockchain for owned UTXO (works only with node configured with an owner key)

However, it happens that the rescan command does work when using a remote node NOT configured with an owner key!

Expected behaviour
The CLI help should say:
rescan the blockchain for owned UTXO (if the node is not configured with an owner key, the full set of current UTXOs will be downloaded for the rescan)

However, please verify first that the above (download of UTXO set) is indeed what happens...

Remark: This issue might be related to #1791

Platform and build

• Tested on CLI Windows
• BEAM Build number: 7.4.1378