Update FAQ release schedule and estimated users (GH-21180)

Update FAQ to include:
* The new yearly release schedule from PEP 602
* Estimated users from "tens of thousands" to "millions"
(cherry picked from commit 3fa4799)

Co-authored-by: E-Paine <63801254+E-Paine@users.noreply.github.com>

Author: miss-islington

Doc/faq/general.rst

@@ -296,8 +296,8 @@ How stable is Python?
 ---------------------
 
 Very stable.  New, stable releases have been coming out roughly every 6 to 18
-months since 1991, and this seems likely to continue.  Currently there are
-usually around 18 months between major releases.
+months since 1991, and this seems likely to continue.  As of version 3.9,
+Python will have a major new release every 12 months (:pep:`602`).
 
 The developers issue "bugfix" releases of older versions, so the stability of
 existing releases gradually improves.  Bugfix releases, indicated by a third
@@ -315,8 +315,8 @@ be maintained after January 1, 2020 <https://www.python.org/dev/peps/pep-0373/>`
 How many people are using Python?
 ---------------------------------
 
-There are probably tens of thousands of users, though it's difficult to obtain
-an exact count.
+There are probably millions of users, though it's difficult to obtain an exact
+count.
 
 Python is available for free download, so there are no sales figures, and it's
 available from many different sites and packaged with many Linux distributions,