Remove guidance on creating local vault in 1PW

Why is this change being made?

1Password 8 seems to have removed the ability to create local, private vaults that can be used to store personal credentials separately from the GitLab managed account. This MR removes the conflicting messaging and indicates that personal credentials can be managed in a separate (paid) account.

Aside: This is a step in the wrong direction, though not by any fault of GitLab. Making it harder for someone to have a secure SSOT for credentials makes it less likely for them to use a password manager in the first place.

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