[sonic-config-engine] Change hwsku for sample graph in unit tests (#10889)

#### Why I did it
To ensure that some internal testcases do not break due to external changes

#### How to verify it
Ran test_cfggen.py with the changes and it passed

Author: neethajohn

src/sonic-config-engine/tests/sample-graph-resource-type.xml

@@ -305,7 +305,7 @@
     <Devices>
       <Device i:type="ToRRouter">
         <Hostname>switch-t0</Hostname>
-        <HwSku>Force10-S6000</HwSku>
+        <HwSku>Arista-7050QX-32S</HwSku>
         <ClusterName>AAA00PrdStr00</ClusterName>
       </Device>
       <Device i:type="LeafRouter">
@@ -742,7 +742,7 @@
       </EthernetInterfaces>
       <FlowControl>true</FlowControl>
       <Height>0</Height>
-      <HwSku>Force10-S6000</HwSku>
+      <HwSku>Arista-7050QX-32S</HwSku>
       <ManagementInterfaces xmlns:a="http://schemas.datacontract.org/2004/07/Microsoft.Search.Autopilot.Evolution">
 	<a:ManagementInterface>
 	  <ElementType>DeviceInterface</ElementType>
@@ -777,5 +777,5 @@
     <Properties xmlns:a="http://schemas.datacontract.org/2004/07/Microsoft.Search.Autopilot.Evolution"/>
   </MetadataDeclaration>
   <Hostname>switch-t0</Hostname>
-  <HwSku>Force10-S6000</HwSku>
+  <HwSku>Arista-7050QX-32S</HwSku>
 </DeviceMiniGraph>