Simplify documentation GH action with custom shell (jump-dev#1227)

* Simplify documentation GH action with custom shell

* Update documentation.yml

Co-authored-by: Oscar Dowson <odow@users.noreply.github.com>

Author: blegat

.github/workflows/documentation.yml

@@ -15,7 +15,11 @@ jobs:
           # Build documentation on Julia 1.0
           version: '1.0'
       - name: Install dependencies
-        run: julia --project=docs/ -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd())); Pkg.instantiate()'
+        shell: julia --project=docs {0}
+        run: |
+          using Pkg
+          Pkg.develop(PackageSpec(path=pwd()))
+          Pkg.instantiate()
       - name: Build and deploy
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} # For authentication with GitHub Actions token