Remove sdk/pullrequest.yml (Azure#39650)

Author: benbp

eng/pipelines/pullrequest.yml

@@ -22,7 +22,7 @@ parameters:
     default: auto
 
 extends:
-  template: ../eng/pipelines/templates/stages/archetype-sdk-client.yml
+  template: /eng/pipelines/templates/stages/archetype-sdk-client.yml
   parameters:
     ServiceDirectory: ${{ parameters.Service }}
     BuildTargetingString: "*"
@@ -31,4 +31,4 @@ extends:
     # See pr->paths->exclude comment above. Anything added/removed there
     # needs to be added/removed here.
     ExcludePaths:
-      - sdk/cosmos
+      - sdk/cosmos