fix: label Solid 2.0 as RC

[brenelz]

Summary

• update the project picker from Solid 2.0 (Beta) to Solid 2.0 (RC)
• align comments and the pending release note with Solid 2.0's release-candidate status

Verification

• pnpm --filter @solid-cli/create build
• pnpm exec vitest run packages/create/tests
• pnpm exec prettier --check packages/create/src/index.ts packages/create/src/utils/constants.ts .changeset/solid-v2-templates.md