Use Trusted Publisher to deploy to PyPI (#160)

Replaces the API tokens. This is the way PyPI recommends deploying.

.github/workflows/pypi.yml

@@ -84,6 +84,10 @@ jobs:
     needs: build
     # Only publish from the origin repository, not forks
     if: github.repository_owner == 'fatiando' && github.event_name != 'pull_request'
+    environment: pypi
+    permissions:
+      # This permission allows trusted publishing to PyPI (without an API token)
+      id-token: write
 
     steps:
       - name: Checkout
@@ -103,10 +107,8 @@ jobs:
       - name: Publish to Test PyPI
         # Only publish to TestPyPI when a PR is merged (pushed to main)
         if: success() && github.event_name == 'push'
-        uses: pypa/gh-action-pypi-publish@bce3b74dbf8cc32833ffba9d15f83425c1a736e0
+        uses: pypa/gh-action-pypi-publish@v1.8.12
         with:
-          user: __token__
-          password: ${{ secrets.TEST_PYPI_TOKEN }}
           repository_url: https://test.pypi.org/legacy/
           # Allow existing releases on test PyPI without errors.
           # NOT TO BE USED in PyPI!
@@ -115,7 +117,4 @@ jobs:
       - name: Publish to PyPI
         # Only publish to PyPI when a release triggers the build
         if: success() && github.event_name == 'release'
-        uses: pypa/gh-action-pypi-publish@bce3b74dbf8cc32833ffba9d15f83425c1a736e0
-        with:
-          user: __token__
-          password: ${{ secrets.PYPI_TOKEN }}
+        uses: pypa/[email protected]