#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/dl.rst b/Doc/library/dl.rst
index 40556cc..92de1dc 100644
--- a/Doc/library/dl.rst
+++ b/Doc/library/dl.rst
@@ -31,7 +31,7 @@
 The :mod:`dl` module defines the following function:
 
 
-.. function:: open(name[, mode=RTLD_LAZY])
+.. function:: open(name, mode=RTLD_LAZY)
 
    Open a shared object file, and return a handle. Mode signifies late binding
    (:const:`RTLD_LAZY`) or immediate binding (:const:`RTLD_NOW`). Default is