simplify preconnect and remove prefetch

[cjyabraham]

#913

Dev instance

This simplifies the preconnect/prefetch function and removes prefetches in favor of preconnect.

Before:

<link rel='dns-prefetch' href='//www.cncf.io' />
<link rel='dns-prefetch' href='//js.hs-scripts.com' />
<link rel='dns-prefetch' href='//cmp.osano.com' />
<link crossorigin='' href='//www.googletagmanager.com' rel='preconnect' />
<link crossorigin='' href='//www.gstatic.com' rel='preconnect' />
<link crossorigin href='//js.hscollectedforms.net' rel='preconnect' />
<link crossorigin href='//js.hs-banner.com' rel='preconnect' />
<link crossorigin href='//js.hs-analytics.net' rel='preconnect' />
<link crossorigin href='//js.hsforms.net' rel='preconnect' />
<link crossorigin href='//js.hs-scripts.com' rel='preconnect' />
<link crossorigin href='//landscape.cncf.io' rel='preconnect' />
<link crossorigin href='//cmp.osano.com' rel='preconnect' />
<link crossorigin href='//consent.api.osano.com' rel='preconnect' />

After:

<link rel='dns-prefetch' href='//pr-914-cncfci.pantheonsite.io' />
<link crossorigin href='//js.hscollectedforms.net' rel='preconnect' />
<link crossorigin href='//js.hs-banner.com' rel='preconnect' />
<link crossorigin href='//js.hs-analytics.net' rel='preconnect' />
<link crossorigin href='//js.hsforms.net' rel='preconnect' />
<link crossorigin href='//js.hs-scripts.com' rel='preconnect' />
<link crossorigin href='//landscape.cncf.io' rel='preconnect' />
<link crossorigin href='//cmp.osano.com' rel='preconnect' />
<link crossorigin href='//consent.api.osano.com' rel='preconnect' />
<link crossorigin href='//www.googletagmanager.com' rel='preconnect' />
<link crossorigin href='//www.gstatic.com' rel='preconnect' />
<link crossorigin href='//browser-update.org' rel='preconnect' />
<link crossorigin href='//js-agent.newrelic.com' rel='preconnect' />