Fix: Corrected the derivation command format

[0xAsten]

Problem

The command for generating a public key is incorrectly formatted, leading to errors when users try to generate keys using the provided syntax.

Here is what I got when execute that example command on Mac terminal:

solana-keygen pubkey prompt://?key=0/1
zsh: no matches found: prompt://?key=0/1

Summary of Changes

Corrected the command syntax.

Fixes #

[jstarry]

@yihau do you know how these docs changes are published? I'm not really sure anymore

[yihau]

iirc bp to beta channel will trigger the pipeline. cc @willhickey

[mergify]

Backports to the beta branch are to be avoided unless absolutely necessary for fixing bugs, security issues, and perf regressions. Changes intended for backport should be structured such that a minimum effective diff can be committed separately from any refactoring, plumbing, cleanup, etc that are not strictly necessary to achieve the goal. Any of the latter should go only into master and ride the normal stabilization schedule. Exceptions include CI/metrics changes, CLI improvements and documentation updates on a case by case basis.

[willhickey]

This PR's change to master will publish to https://edge.docs.anza.xyz/cli/wallets/paper

The v2.0 backport will publish to docs.anza.xyz and and beta.docs.anza.xyz. A v1.18 backport would publish to stable.docs.anaz.xyz but I'm not going to bother... since v1.18 is nearly EOL