fix speling errors

Author: sblondon

Doc/library/mailbox.rst

@@ -77,8 +77,9 @@ Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.
       corrupting the entire mailbox.
 
    The :class:`Mailbox` class supports the :keyword:`with` statement.  When used
-   like this, the Mailbox get a lock when the :keyword:`with` statement enters and
-   release it and :meth:`close` when the :keyword:`with` statement exits.
+   like this, the Mailbox acquires a lock when the :keyword:`with` statement
+   enters and releases it and :meth:`close` when the :keyword:`with` statement
+   exits.
 
    .. versionchanged:: 3.7
       Support for the :keyword:`with` statement was added.