Remove MailPoet premium version from individual calls to trackEvent()

This commit removes the property 'MailPoet Premium version' from all the
calls to MailPoet.trackEvent(). It is not necessary to pass this
property anymore, as since 0a10300625,
this property is included automatically whenever MailPoet send data to
Mixpanel.

[MAILPOET-3885]

assets/js/src/newsletters/automatic_emails/events_conditions.jsx

@@ -116,7 +116,6 @@ class EventsConditions extends React.Component {
       },
     }).done((response) => {
       MailPoet.trackEvent('Emails > New Automatic Email Created', {
-        'MailPoet Premium version': window.mailpoet_premium_version,
         'Event type': options.event,
         'Schedule type': options.afterTimeType,
         'Schedule value': options.afterTimeNumber,

assets/js/src/newsletters/send/ga_tracking.jsx

@@ -4,10 +4,7 @@ import MailPoet from 'mailpoet';
 import ReactStringReplace from 'react-string-replace';
 
 // Track once per page load
-const trackCampaignNameTyped = _.once(() => MailPoet.trackEvent(
-  'User has typed a GA campaign name',
-  { 'MailPoet Premium version': window.mailpoet_premium_version }
-));
+const trackCampaignNameTyped = _.once(() => MailPoet.trackEvent('User has typed a GA campaign name'));
 const tipLink = 'https://kb.mailpoet.com/article/187-track-your-newsletters-subscribers-in-google-analytics';
 const tip = ReactStringReplace(
   MailPoet.I18n.t('gaCampaignTip'),

assets/js/src/newsletters/types/automatic_emails/events_list.jsx

@@ -15,7 +15,6 @@ class AutomaticEmailEventsList extends React.Component {
 
   eventsConfigurator(eventSlug) {
     MailPoet.trackEvent('Emails > Automatic Type selected', {
-      'MailPoet Premium version': window.mailpoet_premium_version,
       'Email type': eventSlug,
     });
     this.props.history.push(`/new/${this.email.slug}/${eventSlug}/conditions`);