Set backing group size to 3

Proposal Summary

• The proposal aims to whitelist a specific referendum on Kusama.
• The referendum can be found at Kusama Referendum 294.
• The proposal involves decoding extrinsic data using Polkadot.js.
• Two examples of decoded extrinsic data are provided.
• The second example was generated using the OpenGov CLI tool.
• The OpenGov CLI tool is available on GitHub.
• The proposal seeks to facilitate the submission of referendums on Kusama.