README: make the 2.0 notice rc-agnostic and link the branch docs

The notice named rc1 and linked the rc1-tagged docs build, going stale
with every release candidate. Generic wording plus the
v2-core-foundation branch docs URL (which tracks the branch tip) means
no README churn for rc2 or any later rc.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: derek73

README.rst

@@ -3,10 +3,11 @@ Name Parser
 
 |Build Status| |PyPI| |PyPI version| |Documentation| |License| |Downloads| |Codecov|
 
-📣 **nameparser 2.0.0rc1 is available for testing** — a new immutable core
-API, with full compatibility for existing code through 2.x. Install it with
-``pip install --pre nameparser`` (a plain install still gets 1.x), read the
-`2.0 docs <https://nameparser.readthedocs.io/en/v2.0.0rc1/>`__, and share
+📣 **A nameparser 2.0 release candidate is available for testing** — a new
+immutable core API, with full compatibility for existing code through 2.x.
+Install it with ``pip install --pre nameparser`` (a plain install still gets
+1.x), read the `2.0 docs
+<https://nameparser.readthedocs.io/en/v2-core-foundation/>`__, and share
 feedback on `the discussion issue
 <https://github.com/derek73/python-nameparser/issues/284>`__.