The maven-gpg-plugin's `gpg.passphrase`/`passphraseServerId` mechanism is
deprecated and fails when the plugin's `bestPractices` mode is enabled.
Stop writing the `gpg.passphrase` server to settings.xml and instead set
`gpg.passphraseEnvName` via an active profile when the configured passphrase
env var name differs from the plugin default (MAVEN_GPG_PASSPHRASE).
The default `gpg-passphrase` input value (GPG_PASSPHRASE) is unchanged, so the
plugin reads the same environment variable as before.
Fixes#760
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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