Make documentation conistent.

Signed-off-by: Mathias L. Baumann <[email protected]>

Author: Marenz

src/frequenz/sdk/timeseries/_ringbuffer.py

@@ -205,7 +205,7 @@ def window(
                 copy of the data.
 
         Raises:
-            IndexError: when requesting a window with invalid timestamps.
+            IndexError: When requesting a window with invalid timestamps.
 
         Returns:
             The requested window