#14804: Remove [] around optional arguments with default values

Mostly just mechanical removal of []. In some rare cases I've pulled the
default value up into the argument list.
diff --git a/Doc/library/timeit.rst b/Doc/library/timeit.rst
index 61e13fe..2b44f91 100644
--- a/Doc/library/timeit.rst
+++ b/Doc/library/timeit.rst
@@ -114,7 +114,7 @@
    time.  This means that other processes running on the same computer may
    interfere with the timing.
 
-.. function:: repeat(stmt[, setup[, timer[, repeat=3 [, number=1000000]]]])
+.. function:: repeat(stmt, setup='pass', timer=default_timer, repeat=3 , number=1000000)
 
    Create a :class:`Timer` instance with the given statement, setup code and timer
    function and run its :meth:`repeat` method with the given repeat count and
@@ -123,7 +123,7 @@
    .. versionadded:: 2.6
 
 
-.. function:: timeit(stmt[, setup[, timer[, number=1000000]]])
+.. function:: timeit(stmt, setup='pass', timer=default_timer, number=1000000)
 
    Create a :class:`Timer` instance with the given statement, setup code and timer
    function and run its :meth:`timeit` method with *number* executions.