remove unnecessary bash indirection

run

@@ -209,13 +209,11 @@ handle_exec() {
         unset start_from_line
       fi
 
-      $as_benchbot bash -c "
-        tmux new-session -d '
+      $as_benchbot tmux new-session -d "
         . ~/.cargo/env &&
         cd \"$install_location\" &&
         yarn &&
         LOG_FORMAT=json LOG_LEVEL_IN_STRING=true LOG_LEVEL=info yarn start 2>&1 1>>\"$exec_log_file\"
-        '
       "
 
       echo -e "\nNote: the command will still be running after quitting this terminal. Use \"run stop\" for stopping it.\n"