Fix incorrect alt text on logo

public/app/core/components/sidemenu/SideMenu.tsx

@@ -17,7 +17,7 @@ export class SideMenu extends PureComponent {
   render() {
     return [
       <div className="sidemenu__logo" onClick={this.toggleSideMenu} key="logo">
-        <img src="public/img/grafana_icon.svg" alt="graphana_logo" />
+        <img src="public/img/grafana_icon.svg" alt="Grafana" />
       </div>,
       <div className="sidemenu__logo_small_breakpoint" onClick={this.toggleSideMenuSmallBreakpoint} key="hamburger">
         <i className="fa fa-bars" />

public/app/core/components/sidemenu/__snapshots__/SideMenu.test.tsx.snap

@@ -8,7 +8,7 @@ Array [
     onClick={[Function]}
   >
     <img
-      alt="graphana_logo"
+      alt="Grafana"
       src="public/img/grafana_icon.svg"
     />
   </div>,