Remove tests for old Spack versions.

Author: jrood-nrel

.github/workflows/tests.yml

@@ -19,10 +19,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version: [3.8, 3.9, 3.12]
-        spack-version: [v0.20.3, v0.21.2, v0.22.5, v0.23.1, develop]
-        exclude:
-          - python-version: 3.12
-            spack-version: v0.20.3
+        spack-version: [develop]
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
@@ -88,10 +85,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version: [3.8, 3.9]
-        spack-version: [v0.20.3, v0.21.2, v0.22.0, v0.22.1, develop]
-        exclude:
-          - python-version: 3.12
-            spack-version: v0.20.3
+        spack-version: [develop]
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
@@ -120,4 +114,3 @@ jobs:
         quick-create --dir unmanaged -s zlib
         spack env deactivate
         quick-create-dev --name develop -s [email protected]
-