fix(ci): replace invalid sign-artifacts input in PyPI publish workflows (#76)

The `sign-artifacts` input is not a valid parameter for
`pypa/gh-action-pypi-publish`. Replace with `attestations: true`
(prod) and remove it (test) to eliminate workflow warnings.

Signed-off-by: jimisola <jimisola@jimisola.com>
Co-authored-by: Jimisola Laursen <jimisola.laursen@resurs.se>

Author: jimisola

.github/workflows/publish_pypi_prod.yml

@@ -34,4 +34,4 @@ jobs:
         # if: startsWith(github.ref, 'refs/tags')
         uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e # v1.13.0
         with:
-          sign-artifacts: true
+          attestations: true

.github/workflows/publish_pypi_test.yml

@@ -31,5 +31,4 @@ jobs:
         uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e # v1.13.0
         with:
           repository-url: https://test.pypi.org/legacy/
-          sign-artifacts: true
           skip-existing: true