refactor: move canView() to UsageGraphs_UsageGraphs

since the permissions required to view admin usage graphs are the same
no matter the section, canView() can be moved to the abstract
UsageGraphs_UsageGraphs class to be used as is by all usagegraph classes

code/web/services/Admin/AbstractUsageGraphs.php

@@ -33,4 +33,11 @@ protected function launchGraph(string $sectionName): void {
 		$this->display('usage-graph.tpl', $graphTitle);
 	}
 
+	public function canView(): bool {
+		return UserAccount::userHasPermission([
+			'View Dashboards',
+			'View System Reports',
+		]);
+	}
+
 }

code/web/services/Admin/UsageGraphs.php

@@ -21,12 +21,6 @@ function getActiveAdminSection(): string {
 		return 'system_reports';
 	}
 
-	function canView(): bool {
-		return UserAccount::userHasPermission([
-			'View Dashboards',
-			'View System Reports',
-		]);
-	}
 
 	public function buildCSV() {
 		global $interface;