#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/formatter.rst b/Doc/library/formatter.rst
index ba09b8e..e696fec 100644
--- a/Doc/library/formatter.rst
+++ b/Doc/library/formatter.rst
@@ -341,10 +341,10 @@
    output.
 
 
-.. class:: DumbWriter([file[, maxcol=72]])
+.. class:: DumbWriter(file=None, maxcol=72)
 
    Simple writer class which writes output on the file object passed in as *file*
-   or, if *file* is omitted, on standard output.  The output is simply word-wrapped
+   or, if *file* is None, on standard output.  The output is simply word-wrapped
    to the number of columns specified by *maxcol*.  This class is suitable for
    reflowing a sequence of paragraphs.