Bump the trunk major version to 12

and clear the release notes.

GitOrigin-RevId: 7ab7b979d29e1e43701cf690f5cf1903740f50e3
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index ab95eae..df3f7ba 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -1,8 +1,8 @@
 =============================
-Release Notes 11.0 (upcoming)
+Release Notes 12.0 (upcoming)
 =============================
 
-In Polly 11 the following important changes have been incorporated.
+In Polly 12 the following important changes have been incorporated.
 
 .. warning::
 
diff --git a/docs/conf.py b/docs/conf.py
index 8b59947..31af9c6 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -49,9 +49,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = '11.0-devel'
+version = '12.0-devel'
 # The full version, including alpha/beta/rc tags.
-release = '11.0-devel'
+release = '12.0-devel'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.