[MNT] fix 0.13.2 release version in pyproject.toml (#542)

Accidentally, `pyproject.toml` was not pushed for the 0.13.2 release.

No upload happened since the CI caught the inconsistency - this just
needs to get fixed.

Author: fkiraly

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "scikit-base"
-version = "0.13.1"
+version = "0.13.2"
 description = "Base classes for sklearn-like parametric objects"
 authors = [
     {name = "sktime developers", email = "sktime.toolbox@gmail.com"},