Don't send issuesSeverity given that's an event default

An event only needs to send this field when overriding the
default. This line is thus unnecessary.

Change-Id: Ia1dfcac5dd25f36f5f4169daf6535fd66aedf754

resources/skins.minerva.scripts/pageIssues.js

@@ -261,8 +261,7 @@
 
 			// Report that the page has been loaded.
 			pageIssuesLogger.log( {
-				action: 'pageLoaded',
-				issuesSeverity: getIssues( KEYWORD_ALL_SECTIONS ).map( formatPageIssuesSeverity )
+				action: 'pageLoaded'
 			} );
 		}