gh-110393: Remove watchdog with hardcoded timeout (#110400)

test_builtin and test_socketserver no longer use signal.alarm() to
implement a watchdog with a hardcoded timeout (2 and 60 seconds).
Python test runner regrtest has two watchdogs: faulthandler and
timeout on running worker processes. Tests using short hardcoded
timeout can fail on slowest buildbots just because the timeout is too
short.

Lib/test/test_builtin.py

@@ -2203,8 +2203,6 @@ class PtyTests(unittest.TestCase):
         if pid == 0:
             # Child
             try:
-                # Make sure we don't get stuck if there's a problem
-                signal.alarm(2)
                 os.close(r)
                 with open(w, "w") as wpipe:
                     child(wpipe)