Issue #25523: Correct "a" article to "an" article

This changes the main documentation, doc strings, source code comments, and a
couple error messages in the test suite. In some cases the word was removed
to fix the grammar.
diff --git a/Doc/library/sqlite3.rst b/Doc/library/sqlite3.rst
index f897234..2b730e8 100644
--- a/Doc/library/sqlite3.rst
+++ b/Doc/library/sqlite3.rst
@@ -583,7 +583,7 @@
    .. attribute:: lastrowid
 
       This read-only attribute provides the rowid of the last modified row. It is
-      only set if you issued a ``INSERT`` statement using the :meth:`execute`
+      only set if you issued an ``INSERT`` statement using the :meth:`execute`
       method. For operations other than ``INSERT`` or when :meth:`executemany` is
       called, :attr:`lastrowid` is set to :const:`None`.