Update strings in contribution statement

Auditors: @luixxiul
Close brave#11309

app/extensions/brave/locales/en-US/preferences.properties

@@ -96,7 +96,7 @@ defaultZoomLevel=Default zoom level
 disableTitleMode=Always show the URL bar
 disconnect=Disconnect
 displayQRCode=Display QR code
-dollarsPaid=$ Paid
+dollarsPaid=Amount
 done=Done
 doNotManageMyPasswords=Don't manage my passwords
 doNotTrack=Send a 'Do Not Track' header with browsing requests *
@@ -242,7 +242,7 @@ paymentsWelcomeText7=for Brave Payments…
 paymentsWelcomeTitle=Welcome to Brave Payments!
 pendingFundsStatus=Pending funds: {{funds}}. Newly-added funds may take 30+ minutes to appear.
 percentage=%
-percentPaid=% Paid
+percentPaid=Percentage
 pl-PL=Polish
 plugins=Plugins
 pluginSettings=Plugin Settings
@@ -385,4 +385,4 @@ visits=Visits
 wideURLbar=Use wide URL bar
 widevine=Run Google Widevine
 widevineSection=Google Widevine Support
-zh-CN=Chinese
+zh-CN=Chinese