Added clarification regarding job mode in V2 (Qiskit#1562)

Closes Qiskit#1486

added a note at https://docs.quantum.ibm.com/run/run-jobs-batch

---------

Co-authored-by: Frank Harkins <frankharkins@hotmail.co.uk>

docs/run/run-jobs-batch.mdx

@@ -46,3 +46,8 @@ The following example shows how you can partition a long list of circuits into m
          job = sampler.run(partitioned_circuits)
          jobs.append(job)
  ```
+
+
+<Admonition type="caution">
+    If you set `backend=backend` in a V2 primitive it will run the program in job mode, even if it's inside a batch/session context. Avoid setting the backend parameter if you want to run in batch/session mode.
+</Admonition>