Update release notes

Signed-off-by: Simon Völcker <simon.voelcker@frequenz.com>

Author: simonvoelcker

RELEASE_NOTES.md

@@ -17,3 +17,5 @@
 - Improved formula validation: Consistent error messages for invalid formulas and conventional span semantics.
 
 - This fixes a rare power distributor bug where some battery inverters becoming unreachable because of network outages would lead to excess power values getting set.  This is fixed by measuring the power of the unreachable inverters through their fallback meters and excluding that power from what is distributed to the other inverters.
+
+- Using more-itertools.peekable instead of our own implementation.