Fix a bunch of "versionchanged" related markup errors.

Doc/library/mailbox.rst

@@ -89,7 +89,8 @@ Maildir, mbox, MH, Babyl, and MMDF.
       format-specific information is used. Otherwise, reasonable defaults for
       format-specific information are used.
 
-      .. versionchanged:: 3.2 support for binary input
+      .. versionchanged:: 3.2
+         Support for binary input was added.
 
 
    .. method:: remove(key)

Doc/library/urllib.request.rst

@@ -902,10 +902,9 @@ FileHandler Objects
    Open the file locally, if there is no host name, or the host name is
    ``'localhost'``.
 
-   This method is applicable only for local hostnames. When a remote hostname
-   is given, an :exc:`URLError` is raised.
-
-.. versionchanged:: 3.2
+   .. versionchanged:: 3.2
+      This method is applicable only for local hostnames.  When a remote
+      hostname is given, an :exc:`URLError` is raised.
 
 
 .. _ftp-handler-objects:

Doc/reference/simple_stmts.rst

@@ -393,7 +393,6 @@ assignment of an empty slice of the right type (but even this is determined by
 the sliced object).
 
 .. versionchanged:: 3.2
-
    Previously it was illegal to delete a name from the local namespace if it
    occurs as a free variable in a nested block.