content/assignments: Update score formatting for async-web-server to fix coding style issue

`run_all.sh` would not be compatible with `grade.sh` causing `grade.sh`
to parse the score incorrectly, leading to wrong coding style scores.

Signed-off-by: Liza Babu <lizza.babu@gmail.com>

tests/run_all.sh

@@ -38,7 +38,7 @@ BEGIN {
 }
 
 END {
-    printf "\n%66s  %3d/100\n", "Total:", sum;
+    printf "\n%s %3d/100\n", "Total:", sum;
 }'
 
 # Cleanup testing environment.