[HTTPS-E Rulesets] Scientific American - removing obsolete rule

[Christopher Liu]

To whom it may concern:

In the Scientific American ruleset, the rule that rewrites current.jpg
to current.cfm appears no longer to be necessary.
The current.jpg image is used near the upper right corner, to show a
sample cover near the "Subscription Center" links.

It also looks like the pagespeed stuff is no longer used, but it's
probably safest to leave it in for another release cycle or so.

It is possible that the ruleset doesn't need to be flagged as mixed
content (all the important scripts/stylesheets seem to be called via
relative paths).

C. Liu