dev-lang/python: revert unnecessary 3.9.0_alpha5 revbump

Bug: https://bugs.gentoo.org/699668
Package-Manager: Portage-2.3.96_p4, Repoman-2.3.22_p1
Signed-off-by: Mike Gilbert <floppym@gentoo.org>

diff --git a/dev-lang/python/python-3.9.0_alpha5-r1.ebuild b/dev-lang/python/python-3.9.0_alpha5.ebuild
similarity index 100%
rename from dev-lang/python/python-3.9.0_alpha5-r1.ebuild
rename to dev-lang/python/python-3.9.0_alpha5.ebuild