Better cope with PowerShell sending a BOM (Windows), or stop trying

[nblumhardt]

Version 5.1.213 includes a small hack to try to get around encoding issues when running seqcli under PowerShell on Windows: https://github.com/datalust/seqcli/blob/dev/src/SeqCli/PlainText/Framing/FrameReader.cs#L39

Unfortunately, this is racy, and doesn't work all the time.

Our options are:

• Dig deeper to figure out how it is that the BOM gets through, even with a UTF-8 encoding specified for STDIN
• Try to skip the BOM in more places (when we read the first line in FrameReader
• Stop trying

I think we're better off giving up; PowerShell Core no longer has this issue (verified with 6.2), so it's a point-in-time thing anyway.