bpo-40744: Drop support for SQLite pre 3.7.3 (GH-20909)

Remove code required to support SQLite pre 3.7.3.

Co-written-by: Berker Peksag <berker.peksag@gmail.com>
Co-written-by: Sergey Fedoseev <fedoseev.sergey@gmail.com>
diff --git a/Doc/library/sqlite3.rst b/Doc/library/sqlite3.rst
index ccb8227..13aa8c5 100644
--- a/Doc/library/sqlite3.rst
+++ b/Doc/library/sqlite3.rst
@@ -18,7 +18,8 @@
 PostgreSQL or Oracle.
 
 The sqlite3 module was written by Gerhard Häring.  It provides a SQL interface
-compliant with the DB-API 2.0 specification described by :pep:`249`.
+compliant with the DB-API 2.0 specification described by :pep:`249`, and
+requires SQLite 3.7.3 or newer.
 
 To use the module, you must first create a :class:`Connection` object that
 represents the database.  Here the data will be stored in the
@@ -591,8 +592,6 @@
          dest = sqlite3.connect(':memory:')
          source.backup(dest)
 
-      Availability: SQLite 3.6.11 or higher
-
       .. versionadded:: 3.7
 
 
@@ -701,9 +700,6 @@
       statements because we cannot determine the number of rows a query produced
       until all rows were fetched.
 
-      With SQLite versions before 3.6.5, :attr:`rowcount` is set to 0 if
-      you make a ``DELETE FROM table`` without any condition.
-
    .. attribute:: lastrowid
 
       This read-only attribute provides the rowid of the last modified row. It is