Updated SC2237 (markdown)

SC2237.md

@@ -20,13 +20,15 @@ if [ -n "$STY" ];       then echo "You are already running screen"; fi
 
 You have negated `test -z` or `test -n`, resulting in a needless double-negative. You can just use the other operator instead:
 
-    # Identical tests to verify that a value is assigned
-    ! [ -z foo ] # Not has no value
-    [ -n foo ]   # Has value
+```sh
+# Identical tests to verify that a value is assigned
+! [ -z foo ] # Not has no value
+[ -n foo ]   # Has value
 
-    # Identical tests to verify that a value is empty
-    ! [ -n foo ] # Not is non-empty
-    [ -z foo ]   # Is empty
+# Identical tests to verify that a value is empty
+! [ -n foo ] # Not is non-empty
+[ -z foo ]   # Is empty
+```
 
 ### Exceptions: