Fixed typo issue and added missing header in customer sales order grid

Author: vishal-7037

app/code/Magento/Customer/Block/Adminhtml/Edit/Tab/Orders.php

@@ -107,7 +107,7 @@ protected function _prepareCollection()
      */
     protected function _prepareColumns()
     {
-        $this->addColumn('increment_id', ['header' => __('Order'), 'width' => '100', 'index' => 'increment_id']);
+        $this->addColumn('increment_id', ['header' => __('Order #'), 'width' => '100', 'index' => 'increment_id']);
 
         $this->addColumn(
             'created_at',
@@ -140,7 +140,7 @@ protected function _prepareColumns()
             $this->addColumn(
                 'action',
                 [
-                    'header' => ' ',
+                    'header' => 'Action',
                     'filter' => false,
                     'sortable' => false,
                     'width' => '100px',

app/code/Magento/Customer/i18n/en_US.csv

@@ -47,7 +47,7 @@ Sending,Sending
 Paused,Paused
 View,View
 Unknown,Unknown
-Order,Order
+"Order #","Order #"
 Purchased,Purchased
 "Bill-to Name","Bill-to Name"
 "Ship-to Name","Ship-to Name"