added max-widths to explore start pages boxes

public/app/plugins/datasource/logging/components/LoggingStartPage.tsx

@@ -8,7 +8,7 @@ interface Props {
 export default class LoggingStartPage extends PureComponent<Props> {
   render() {
     return (
-      <div className="grafana-info-box">
+      <div className="grafana-info-box grafana-info-box--max-lg">
         <LoggingCheatSheet onClickExample={this.props.onClickExample} />
       </div>
     );

public/app/plugins/datasource/prometheus/components/PromStart.tsx

@@ -8,7 +8,7 @@ interface Props {
 export default class PromStart extends PureComponent<Props> {
   render() {
     return (
-      <div className="grafana-info-box">
+      <div className="grafana-info-box grafana-info-box--max-lg">
         <PromCheatSheet onClickExample={this.props.onClickExample} />
       </div>
     );

public/sass/components/_infobox.scss

@@ -32,6 +32,10 @@
   a {
     @extend .external-link;
   }
+
+  &--max-lg {
+    max-width: map-get($grid-breakpoints, 'lg');
+  }
 }
 
 .grafana-info-box__close {