examples/micropython: fix checked PID

With #14224 the idle thread became
optional, so the main thread can have either 1 or 2 as PID, depending
if the idle thread is included or not. As this might also change in the
future, it is probably the best to just expect any number.

examples/micropython/tests/01-run.py

@@ -22,7 +22,7 @@ def get_time():
     # test riot.thread_getpid()
     child.sendline('import riot')
     child.sendline('print(riot.thread_getpid())')
-    child.expect_exact('2')
+    child.expect(r'\d+')
     child.expect_exact('>>>')
 
     #