Fix help text test for FSI

[dsyme]

It seems from a failure in #5790 that the "fsharpqa" help-text checks for FSI.EXE aren't running correctly. They were either failing silently because fsi.exe was not found on the path or something else is going on.

The help text is also messed up because the minimum column width was not set correctly (if you run fsc.exe --help you'll see what I mean).

I'm not quite sure why this hasn't been detected for the fsc.exe help text test.

[dsyme]

Note the help text in the updated baseline looks more squashed because it tests using 80 columns and that's now a bit squashed. But that's actually correct - and since most terminals are now 120 columns the help text looks ok.

[dsyme]

Before (wrapping lines):

After (no wrapping lines)