update severity, testCaseId

Author: engcom-Charlie

app/code/Magento/Sales/Test/Mftf/Test/AdminOpenCreditmemoViewPageWithWrongCreditmemoIdTest.xml

@@ -13,7 +13,8 @@
             <stories value="Creditmemo Page With Wrong Creditmemo Id"/>
             <title value="Open Creditmemo View Page with Wrong Creditmemo Id"/>
             <description value="Open Creditmemo View Page with Wrong Creditmemo Id."/>
-            <severity value="MAJOR"/>
+            <severity value="BLOCKER"/>
+            <testCaseId value="MC-39500"/>
             <group value="sales"/>
         </annotations>
         <before>