remove header background image (#4850)

frontend/src/metabase/css/home.css

@@ -2,15 +2,6 @@
     z-index: 4;
 }
 
-.CheckBg {
-    background-image: url('/app/components/icons/assets/header_rect.svg');
-    background-repeat: repeat;
-}
-
-.CheckBg-offset {
-  background-position-y: -15px;
-}
-
 .NavItem {
     border-radius: 8px;
 }

frontend/src/metabase/home/containers/HomepageApp.jsx

@@ -77,7 +77,7 @@ export default class HomepageApp extends Component {
                     </Modal>
                 : null }
 
-                <div className="CheckBg bg-brand text-white md-pl4">
+                <div className="bg-brand text-white md-pl4">
                     <div style={{marginRight: 346}}>
                         <div className="Layout-mainColumn">
                             <header style={this.styles.headerGreeting} className="flex align-center pb4 pt1">

frontend/src/metabase/nav/containers/Navbar.jsx

@@ -118,7 +118,7 @@ export default class Navbar extends Component {
 
     renderMainNav() {
         return (
-            <nav className={cx("Nav CheckBg CheckBg-offset relative bg-brand sm-py2 sm-py1 xl-py3", this.props.className)}>
+            <nav className={cx("Nav relative bg-brand sm-py2 sm-py1 xl-py3", this.props.className)}>
                 <ul className="ml2 sm-pl4 pr1 flex align-center">
                     <li>
                         <Link to="/" data-metabase-event={"Navbar;Logo"} className="NavItem cursor-pointer text-white flex align-center my1 transition-background p1">

resources/frontend_client/app/components/icons/assets/header_rect.svg

-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<svg width="58px" height="57px" viewBox="0 0 58 57" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
-    <g stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
-        <g transform="translate(-393.000000, -53.000000)" fill="#4F9CE0">
-            <g transform="translate(-6.000000, -9.000000)">
-                <g transform="translate(13.000000, -3.000000)">
-                    <rect transform="translate(415.000000, 93.715729) rotate(-45.000000) translate(-415.000000, -93.715729) " x="395" y="73.7157288" width="40" height="40"></rect>
-                </g>
-            </g>
-        </g>
-    </g>
-</svg>