Add note to Apache docs to update WSGIScriptAlias directive for Python 3.8+ to fix "RuntimeError: fork not supported for subinterpreters"

[schwemmer]

See the following links for more information about how Python 3.8 started to prohibit fork() calls in subinterpreters

• https://github.com/GrahamDumpleton/mod_wsgi/issues/614
• https://bugs.python.org/issue37951
• https://bugzilla.redhat.com/show_bug.cgi?id=1745894