Clear release notes for 18.x

GitOrigin-RevId: 4706251a3186c34da0ee8fd894f7e6b095da8fdc
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 804e2a5..61bee08 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -1,5 +1,5 @@
 =======================================
-PSTL 17.0.0 (In-Progress) Release Notes
+PSTL 18.0.0 (In-Progress) Release Notes
 =======================================
 
 .. contents::
@@ -30,7 +30,7 @@
 To see the release notes for a specific release, please see the `releases
 page <https://llvm.org/releases/>`_.
 
-What's New in PSTL 17.0.0?
+What's New in PSTL 18.0.0?
 ==========================
 
 New Features