test.yaml: use shaperglot prerelease

.github/workflows/test.yaml

diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 2843ccb..d419bc7 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -29,6 +29,7 @@
       - name: Install packages
         run: |
           pip install gftools[qa] pytest
+          pip install -U --pre shaperglot
         shell: bash
       - name: Setup Chrome
         uses: browser-actions/setup-chrome@v1.6.2