Update docstring per review to clarify new file

Author: ArBridgeman

exasol/toolbox/util/release/changelog.py

@@ -77,7 +77,7 @@ def update_changelogs_for_release(self) -> None:
         Rotates the changelogs as is needed for a release.
 
           1. Moves the contents of the `unreleased.md` to the `changes_<version>.md`
-          2. Create a new `unreleased.md`
+          2. Create a new file `unreleased.md`
           3. Updates the table of contents in the `changelog.md` with the new `changes_<version>.md`
         """