Let bin/brew handle its own exporting

[Bo98]

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If HOMEBREW_NO_ENV_FILTERING is not set, then /usr/bin/env already exports these. For consistency, we should be doing the same if HOMEBREW_NO_ENV_FILTERING is set.

[BrewTestBot]

Review period will end on 2021-03-03 at 17:02:13 UTC.

[BrewTestBot]

Review period ended.