Update pragma check: validate by actually running the compiler (#5730)

Co-authored-by: Arr00 <13561405+arr00@users.noreply.github.com>

.github/workflows/checks.yml

@@ -41,8 +41,8 @@ jobs:
         run: npm run test
       - name: Check linearisation of the inheritance graph
         run: npm run test:inheritance
-      - name: Check pragma consistency between files
-        run: npm run test:pragma
+      - name: Check pragma validity
+        run: npm run test:pragma -- --concurrency 1
       - name: Check procedurally generated contracts are up-to-date
         run: npm run test:generation
       - name: Compare gas costs