add patch notes

hypothesis-python/RELEASE.rst

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+RELEASE_TYPE: patch
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+This patch improves our error and warning messages.
+
+- Add a warning for ``st.text("ascii")`` - you probably meant ``st.text(st.characters(codec="ascii"))``. Similarly for ``"utf-8"``.
+- Recommend remedies in the error message of ``Unsatisfiable``.
+- When ``@given`` errors because it was given an extra keyword argument, and the keyword matches a setting name like ``max_examples``, recommend ``@settings(max_examples=...)`` instead.