Update Quay's packages for Python 3.9 compatibility

Background

Quay v3.4.0 is targeting compatibility with Python 3.8. This version of Python has been stable for over a year. We don't want to fall too far behind on our package bumps and Python compatibility. That contributed towards the massive Python 2.7 -> Python 3.8 migration that we have spent the majority of a year working on.

After some simple experiments in Fedora 33, which uses Python 3.9 by default, I have found that only a handful of packages need to be updated to successfully pass `pip install -r requirements.txt`. This is not indicative of how well Quay will function under Python 3.9, however.

Requirements

• Quay and all of its dependencies can be successfully installed and work as expected when using Python 3.9.
• The Continuous Integration tests cover both Python 3.8 and Python 3.9 in the test matrix.

Example Changes

The following diff shows some simple changes I made to Quay's requirements.txt file to successfully install all Python dependencies in Python 3.9.

$ git diff python3.9 upstream/master -- requirements.txt
diff --git a/requirements.txt b/requirements.txt
index 7fefb7fa..1f0ba07c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -40,8 +40,8 @@ docker==4.1.0
 docutils==0.15.2
 dumb-init==1.2.2
 ecdsa==0.15
-elasticsearch==7.9.1
-elasticsearch-dsl==7.3.0 # TODO: double-check that this is required
+elasticsearch==7.0.4
+elasticsearch-dsl==7.0.0
 fakeredis==1.1.0
 Flask==1.1.1
 Flask-Cors==3.0.8
@@ -55,10 +55,10 @@ furl==2.1.0
 future==0.18.2
 futures==3.1.1
 geoip2==3.0.0
-gevent==20.9.0
+gevent==1.4.0
 gipc==1.0.1
-greenlet==0.4.17
-grpcio==1.33.2
+greenlet==0.4.15
+grpcio==1.30.0
 gunicorn==20.0.4
 hashids==1.2.0
 hiredis==1.0.1
@@ -139,7 +139,7 @@ recaptcha2==0.1
 redis==3.3.11
 redlock==1.2.0
 rehash==1.0.0
-reportlab==3.5.55
+reportlab==3.5.34
 requests==2.22.0
 requests-aws4auth==0.9
 requests-file==1.4.3