bpo-36205: Fix the rusage implementation of time.process_time() (GH-15538)

(cherry picked from commit 8bf5fef8737fdd12724b9340d76a4ed391c4ad8a)

Co-authored-by: vrajivk <3413293+vrajivk@users.noreply.github.com>
diff --git a/Modules/timemodule.c b/Modules/timemodule.c
index bdc93a2..5e0010c 100644
--- a/Modules/timemodule.c
+++ b/Modules/timemodule.c
@@ -1208,7 +1208,7 @@
             return -1;
         }
 
-        _PyTime_t total = utime + utime;
+        _PyTime_t total = utime + stime;
         *tp = total;
         return 0;
     }