alerting: removed width restriction on message, fixes #8000

public/app/features/alerting/partials/alert_tab.html

@@ -129,7 +129,7 @@
 			</div>
 			<div class="gf-form gf-form--v-stretch">
 				<span class="gf-form-label width-8">Message</span>
-				<textarea class="gf-form-input width-20" rows="10" ng-model="ctrl.alert.message"  placeholder="Notification message details..."></textarea>
+				<textarea class="gf-form-input" rows="10" ng-model="ctrl.alert.message"  placeholder="Notification message details..."></textarea>
 			</div>
 		</div>