Clarify that the shifting matrioshka docs are only for batteries

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

src/frequenz/sdk/microgrid/__init__.py

@@ -186,6 +186,11 @@
 method available for all pools, which also streams the bounds that an actor
 should comply with, based on its priority.
 
+### Working with other actors to control Batteries
+
+This section describes the details of the power manager's reconciliation
+algorithm for controlling batteries.
+
 #### Adding the power proposals of individual actors
 
 When an actor A calls the `propose_power` method with a power, the proposed