ci: use VJOBS=1 for alpine docker format check (#19762)

Author: ttytm

.github/workflows/containers_ci.yml

@@ -50,7 +50,7 @@ jobs:
         run: CC=gcc make
 
       - name: All code is formatted
-        run: ./v test-cleancode
+        run: VJOBS=1 ./v test-cleancode
 
       - name: Run only essential tests
         run: VTEST_JUST_ESSENTIAL=1 ./v test-self