Prevent triggering wp_print_scripts action when printing component scripts for legacy templates

[Weston Ruter]

In #1097 we eliminated use of wp_print_scripts() in favor of wp_scripts()->do_items() to prevent triggering the wp_print_scripts action, which some plugins use to output scripts to the page. This change, however, was not done similarly when printing scripts for legacy templates:

https://github.com/Automattic/amp-wp/blob/70711f0cd647f233b02ffa1bbbd58496eeeea510/includes/amp-post-template-actions.php#L67-L70

This results in a support topic like this: https://wordpress.org/support/topic/slidedeck-js-not-being-stripped/

[Weston Ruter]

This issue is starting to blow up in the support forums and it needs to be prioritized:

• https://wordpress.org/support/topic/custom-javascript-is-not-allowed/
• https://wordpress.org/support/topic/server-error-5xx-on-amp-pages/
• https://wordpress.org/support/topic/custom-javascript-is-not-allowed-2/
• https://wordpress.org/support/topic/js-created-by-the-user-of-the-page/
• https://wordpress.org/support/topic/javascript-rejected-by-google-adsense/
• https://wordpress.org/support/topic/slidedeck-js-not-being-stripped/

The PR opened should be confirmed to fix the above issues.

We should release v0.7.2 this week.