Fix Unguarded actions library use code scanning error

Must access the env var directly in order to avoid recursive calls to 
`getRequiredEnvParam`.

lib/util.js

@@ -396,7 +396,9 @@ function getRequiredEnvParam(paramName) {
     if (value === undefined || value.length === 0) {
         throw new Error(`${paramName} environment variable must be set`);
     }
-    core.debug(`${paramName}=${value}`);
+    if (process.env[EnvVar.RUN_MODE] === Mode.actions) {
+        core.debug(`${paramName}=${value}`);
+    }
     return value;
 }
 exports.getRequiredEnvParam = getRequiredEnvParam;