env_config: Improve the deprecated envvar message

[issyl0]

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Before:

❯ HOMEBREW_NO_ANALYTICS=0 brew formula-analytics --days-ago=2
Error: Calling HOMEBREW_NO_ANALYTICS=0 is deprecated! Use If you wish to enable HOMEBREW_NO_ANALYTICS, use HOMEBREW_NO_ANALYTICS=1
If you wish to disable HOMEBREW_NO_ANALYTICS, use HOMEBREW_NO_ANALYTICS= instead.

After:

❯ HOMEBREW_NO_ANALYTICS=0 brew formula-analytics --days-ago=2
Error: Calling HOMEBREW_NO_ANALYTICS=0 is deprecated! Use HOMEBREW_NO_ANALYTICS=1 to enable and HOMEBREW_NO_ANALYTICS= (an empty value) to disable instead.

[p-linnane]

Makes sense. Thanks!

[MikeMcQuaid]

Thanks, works for me!