CI: fix images/commands used for pypi dist build job

.ci/build_pypi_dist.sh

@@ -2,8 +2,6 @@
 
 set -e
 
-source /test.venv/bin/activate
-
 pip install --upgrade pip wheel setuptools twine build
 
 python -m build

.gitlab-ci.yml

@@ -180,7 +180,7 @@ test:3.11:
 
 test:build-pypi-dist:
   stage: test
-  image: pauldmccarthy/fsleyes-py310-wxpy4-gtk3
+  image: python:3.10
   except:
     - tags
 
@@ -188,7 +188,6 @@ test:build-pypi-dist:
     - docker
 
   script:
-   - source /test.venv/bin/activate
    - bash ./.ci/build_pypi_dist.sh