#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/pickletools.rst b/Doc/library/pickletools.rst
index ce47c97..ebb30ab 100644
--- a/Doc/library/pickletools.rst
+++ b/Doc/library/pickletools.rst
@@ -20,7 +20,7 @@
 probably won't find the :mod:`pickletools` module relevant.
 
 
-.. function:: dis(pickle[, out=None, memo=None, indentlevel=4])
+.. function:: dis(pickle, out=None, memo=None, indentlevel=4)
 
    Outputs a symbolic disassembly of the pickle to the file-like object *out*,
    defaulting to ``sys.stdout``.  *pickle* can be a string or a file-like object.