Apply suggestions from code review

Co-authored-by: daniel-zullo-frequenz <[email protected]>
Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -10,9 +10,9 @@
 
    ```python
    # Old
-   actor = ConfigManagingActor(config_file="config.yaml")
+   actor = ConfigManagingActor(config_file="config.toml")
    # New
-   actor = ConfigManagingActor(config_files=["config.yaml"])
+   actor = ConfigManagingActor(config_files=["config.toml"])
    ```
 
 ## New Features

src/frequenz/sdk/config/_config_managing.py

@@ -25,7 +25,7 @@ class ConfigManagingActor(Actor):
     When the actor is started the configuration files will be read and sent to the
     output sender. Then the actor will start monitoring the files for updates.
 
-    If no configuration file could be read, the actor will raise a exception.
+    If no configuration file could be read, the actor will raise an exception.
 
     The configuration files are read in the order of the paths, so the last path will
     override the configuration set by the previous paths. Dict keys will be merged