MDL-74188 notes: consistent formatting of text content.

Each method of adding notes, either via UI or external service (via
course participant actions), defined the format of the content
different from one another. Neither of those formats were correct.

notes/lib.php

@@ -108,7 +108,7 @@ function note_save(&$note) {
     $note->lastmodified = time();
     $note->usermodified = $USER->id;
     if (empty($note->format)) {
-        $note->format = FORMAT_PLAIN;
+        $note->format = FORMAT_MOODLE;
     }
     if (empty($note->publishstate)) {
         $note->publishstate = NOTES_STATE_PUBLIC;