Fix up some minor spicy tutorial docs

[evantypanski]

This is just what I found going through the tutorial myself

1. The initial command zeek - N Zeek::Spicy has an extra space so that command is invalid
2. Line numbers are wrong because the tftp.evt file added two new lines at the top I think. Its current state looks like:

It should (and does after this) look like:

3. Added an import spicy; mention since I personally prefer everything needed to compile a program being somewhere in the tutorial. It is in the complete grammar at the end of the spicy tutorial, though, but I prefer a mention in the zeek integration too (since it was never mentioned in the actual spicy tutorial)

[timwoj]

It should (and does after this) look like:

This is going to be wrong again in about 30 minutes after I remove the deprecated port field. It was marked as deprecated in 7.0 and we're removing support entirely in 7.1.

[timwoj]

This looks fine to me. We'll need to make the associated deprecation fixes and update the line numbers again for tftp.evt, but that can be separate from this PR.

[rsmmr]

Nice, thanks! Just one small tweak for clarity.