2.15.0: Remove pre-release warning (#1419)

Author: joshmoore

docs/release.rst

@@ -1,6 +1,13 @@
 Release notes
 =============
 
+..
+    # Copy the warning statement _under_ the latest release version
+    # and unindent for pre-releases.
+
+    .. warning::
+       Pre-release! Use :command:`pip install --pre zarr` to evaluate this release.
+
 ..
     # Unindent the section between releases in order
     # to document your changes. On releases it will be
@@ -16,9 +23,6 @@ Release notes
 2.15.0
 ------
 
-.. warning::
-   Pre-release! Use :command:`pip install --pre zarr` to evaluate this release.
-
 Enhancements
 ~~~~~~~~~~~~