Iframe clean

[xmontana]

Format text summary and fullsummary allowing trusted text like <iframe> if enabletrusttext is enabled. Related to issue #87

[institut-agro-ead]

The use of format_text for summary and fullcontent has been added with v4.1.4 but seems to be useless ?
format_text is already called in moodle core via $this->courseformatdatacommontrait->course_section_cm_text or $renderer->format_summary_text meaning the module content is already formatted once (with noclean option set to true) then the result is once again formatted without the noclean option. Iframes disappear, so H5Ps embeded inside labels via the H5P button inside text editor don’t show.
Basically, I think those lines should simply be removed as they weren’t here before v4.1.4 and seem to be redundant.