Make downgrade test dev inside test env

Previously, ClimaCore was dev'd before entering the
test env.

.github/workflows/Downstream.yml

@@ -46,27 +46,10 @@ jobs:
           repository: 'CliMA/${{ matrix.package }}'
           path: ${{ matrix.package }}
 
-      # The test suite for ClimaTimesteppers depends on ClimaCore, not
-      # ClimaTimesteppers itself. If we dev-ed ClimaCore in ClimaTimesteppers,
-      # the aqua test would fail because we never use ClimaCore. The same applies for ClimaUtilities.
-      - if: (matrix.package != 'ClimaTimesteppers.jl' && matrix.package != 'ClimaCoupler.jl' &&
-      matrix.package != 'ClimaUtilities.jl')
+      - if: (matrix.package != 'ClimaCoupler.jl')
         run: |
           julia --color=yes --project=${{ matrix.package }} -e 'using Pkg; Pkg.instantiate()'
-          julia --color=yes --project=${{ matrix.package }} -e 'using Pkg; Pkg.develop(; path = ".")'
-          julia --color=yes --project=${{ matrix.package }} -e 'using Pkg; Pkg.test()'
-
-      - if: matrix.package == 'ClimaTimesteppers.jl'
-        run: |
-          julia --color=yes --project=ClimaTimesteppers.jl/test -e 'using Pkg; Pkg.instantiate()'
-          julia --color=yes --project=ClimaTimesteppers.jl/test -e 'using Pkg; Pkg.develop(; path = ".")'
-          julia --color=yes --project=ClimaTimesteppers.jl/test ClimaTimesteppers.jl/test/runtests.jl
-
-      - if: matrix.package == 'ClimaUtilities.jl'
-        run: |
-          julia --color=yes --project=ClimaUtilities.jl/test -e 'using Pkg; Pkg.instantiate()'
-          julia --color=yes --project=ClimaUtilities.jl/test -e 'using Pkg; Pkg.develop(; path = ".")'
-          julia --color=yes --project=ClimaUtilities.jl/test ClimaUtilities.jl/test/runtests.jl
+          julia --color=yes --project=${{ matrix.package }} -e 'using Pkg; Pkg.test(; julia_args = "-e using Pkg; Pkg.develop(; path = \".\")")'
 
       - if: matrix.package == 'ClimaCoupler.jl'
         run: |