Update Firely.Terminal pipeline to v0.7.20-alpha1

Bump the Firely.Terminal GitHub Actions pipeline version from v0.7.18 to v0.7.20-alpha1 for improved features and fixes.

Author: ArdonToonstra

.github/workflows/stu3_firely_terminal.yaml

@@ -38,7 +38,7 @@ jobs:
           java-version: '21'
 
       - name: Firely.Terminal (GitHub Actions)
-        uses: FirelyTeam/firely-terminal-pipeline@v0.7.18
+        uses: FirelyTeam/firely-terminal-pipeline@v0.7.20-alpha1
         with:
           PATH_TO_CONFORMANCE_RESOURCES: input/resources
           PATH_TO_EXAMPLES: input/resources