We should extend the timeout of this buildbot worker.

More and more tests are failing randomly with the 15 min timeout:

https://buildbot.python.org/all/#/builders/58/builds/2060

0:19:49 [ 36/420/1] test_zipfile crashed (Exit code 1) -- running: test_multiprocessing_spawn (14 min 19 sec)
Timeout (0:15:00)!
Thread 0x00000a94 (most recent call first):
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\zipfile.py", line 603 in _init
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\zipfile.py", line 610 in compress
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\zipfile.py", line 1100 in write
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\test\test_zipfile.py", line 65 in make_test_archive
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\test\test_zipfile.py", line 257 in zip_readlines_test
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\test\test_zipfile.py", line 268 in test_readlines
...

0:20:33 [ 41/420/2] test_multiprocessing_spawn crashed (Exit code 1)
Timeout (0:15:00)!
Thread 0x00000b2c (most recent call first):
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\multiprocessing\connection.py", line 810 in _exhaustive_wait
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\multiprocessing\connection.py", line 878 in wait
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\multiprocessing\connection.py", line 330 in _poll
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\multiprocessing\connection.py", line 257 in poll
  File "D:\cygwin\home\db3l\buildarea\3.x.bolen-windows7\build\lib\test\_test_multiprocessing.py", line 3261 in test_strings