README: retitle, add note

Signed-off-by: William Woodruff <william@trailofbits.com>

README.md

@@ -62,12 +62,17 @@ The secret used in `${{ secrets.PYPI_API_TOKEN }}` needs to be created on the
 settings page of your project on GitHub. See [Creating & using secrets].
 
 
-### Publishing with OpenID Connect
+### Trusted publishing
 
 > **IMPORTANT**: This functionality is in beta, and will not work for you
 > unless you're a member of the PyPI trusted publishing beta testers' group.
 > For more information, see [warehouse#12965].
 
+> **NOTE**: Trusted publishing is sometimes referred to by its
+> underlying technology -- OpenID Connect, or OIDC for short.
+> If you see references to "OIDC publishing" in the context of PyPI,
+> this is what they're referring to.
+
 This action supports PyPI's [trusted publishing]
 implementation, which allows authentication to PyPI without a manually
 configured API token or username/password combination. To perform