Fix typo / copy pasta in example Pipeline

We renamed `inputSourceBindings` (and `outputSourceBindings`) to
`resources` in tektoncd#148 where we also moved the specification of these
bindings into the `PipelineRun` - now the `resources` section in the
`Pipeline` itself exists just to specify dependencies between resources.

But we missed one in the example!

Also created tektoncd#297 to follow up on catching this in validation.

examples/pipeline.yaml

@@ -38,7 +38,7 @@ spec:
   - name: deploy-web
     taskRef:
       name: demo-deploy-kubectl
-    inputSourceBindings:
+    resources:
     - name: image
       providedBy:
       - build-skaffold-web