CI: Don’t use root working directory

I think this was breaking the dependabot runs, because “/” was
interpreted here as the root directory of the runner, not the top level
of the repository, and there wasn’t permission to create files and
directories there. Probably this worked at first and only broke
recently.

.github/workflows/dependabot.yml

@@ -46,7 +46,6 @@ jobs:
 
       - name: Install - support-reminders
         run: yarn
-        working-directory: /
 
       - name: Install - CDK
         run: yarn
@@ -55,7 +54,6 @@ jobs:
       # ---- Build ---- #
       - name: Build - support-reminders
         run: yarn run build
-        working-directory: /
 
 
       - name: Build - CDK
@@ -65,7 +63,6 @@ jobs:
       # ---- Test ---- #
       - name: Test - support-reminders
         run: yarn run test
-        working-directory: /
         env:
           TEST_DB_URL: postgresql://localhost/postgres
           TEST_DB_USER: postgres