Remove bitdefender diagnostic check

[apainintheneck]

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This check was added in four years ago in #5614. We were seeing problems at the time with users not being able to download packages correctly when running BitDefender (#4579 and #5558).

Those issues were apparently resolved by BitDefender and we got an issue in mid 2020 asking us to remove the check since it was no longer necessary (#7452). Since that point we haven't received anymore issues or complaints related to BitDefender in either the main brew repo or in the discussions (I just searched for bitdefender in both places).

Also, anecdotally, I haven't had any problems using brew and BitDefender at the same time on my local system.

CC: @MikeMcQuaid since you added the check and were involved in previous discussions.

[BrewTestBot]

Review period will end on 2022-12-29 at 19:04:45 UTC.

[MikeMcQuaid]

Fine with me. Should re-add the minute anything related crops up again.

[BrewTestBot]

Review period ended.