Update onboarding-library.md

[Nahee-Park]

Replace ethereum.off with ethereum.removeListener
MetaMask/metamask-extension#10873 (comment)

[sigridjineth]

Great work from @Nahee-Park 👍 The docs seem to be required more attention from developers to have up-to-date content. The issue was once claimed from the following issue, but not reflected correctly in the documentation.

I hope for ppl to avoid any possible holes staggering into the issue. In addition, it was once suggested from the EIP-1193 protocol suggestion link.

The code below has its reference.

provider.on("accountsChanged", handleAccountsChanged)

function handleAccountsChanged() {
  // do something
}

// When leaving the page (Vue 3 - Composition API)
onUnmounted(() => {
  if (provider.removeListener) {
    provider.removeListener("accountsChanged", handleAccountsChanged)
  }
})

[BboyAkers]

LGTM! Thanks for catching this 🙂