Rewards on Desktop: Remove temporary header

Now that Brave-Core has its own Navigation Bar (implemented in brave/brave-core#1422), we can remove the temporary reserved area from the Rewards Views.
Required for brave/brave-browser#956

src/features/rewards/settingsPage/__snapshots__/spec.tsx.snap

@@ -9,11 +9,6 @@ exports[`SettingsPage tests basic tests matches the snapshot 1`] = `
 }
 
 .c1 {
-  background-image: linear-gradient(267deg,#bf14a2,#f73a1c);
-  height: 62px;
-}
-
-.c2 {
   max-width: 1000px;
   margin: 0 auto;
   padding: 40px 0;
@@ -26,8 +21,5 @@ exports[`SettingsPage tests basic tests matches the snapshot 1`] = `
   <div
     className="c1"
   />
-  <div
-    className="c2"
-  />
 </div>
 `;

src/features/rewards/settingsPage/index.tsx

@@ -3,7 +3,7 @@
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import * as React from 'react'
-import { StyledWrapper, StyleHeader, StyledContent } from './style'
+import { StyledWrapper, StyledContent } from './style'
 
 export interface Props {
   id?: string
@@ -16,7 +16,6 @@ export default class SettingsPage extends React.PureComponent<Props, {}> {
 
     return (
       <StyledWrapper id={id}>
-        <StyleHeader />
         <StyledContent>
           {children}
         </StyledContent>

src/features/rewards/settingsPage/style.ts

@@ -11,11 +11,6 @@ export const StyledWrapper = styled<{}, 'div'>('div')`
   font-family: "Poppins", sans-serif
 `
 
-export const StyleHeader = styled<{}, 'div'>('div')`
-  background-image: linear-gradient(267deg, #bf14a2, #f73a1c);
-  height: 62px;
-`
-
 export const StyledContent = styled<{}, 'div'>('div')`
  max-width: 1000px;
  margin: 0 auto;