fix: remove job count from parallel mode debug log (#4416)

Author: sujin-park

lib/cli/run-helpers.js

@@ -141,11 +141,7 @@ const singleRun = async (mocha, {exit}, fileCollectParams) => {
  */
 const parallelRun = async (mocha, options, fileCollectParams) => {
   const files = collectFiles(fileCollectParams);
-  debug(
-    'executing %d test file(s) across %d concurrent jobs',
-    files.length,
-    options.jobs
-  );
+  debug('executing %d test file(s) in parallel mode', files.length);
   mocha.files = files;
 
   // note that we DO NOT load any files here; this is handled by the worker