Update PyGreSQL from pre-release to 5.2.0

PyGreSQL 5.2.0 which contains the fixes submitted and referenced in
cb8d54a6 was released on June 21, 2020.

Update the build process to use this tagged release rather than a
pre-release hash
Authored-by: NTyler Ramer <tramer@vmware.com>

gpMgmt/bin/Makefile

@@ -71,7 +71,7 @@ endif
 #
 # PyGreSQL
 #
-PYGRESQL_VERSION=b1e040e989b5b1b75f42c1103562bfe8f09f93c3
+PYGRESQL_VERSION=5.2
 PYGRESQL_DIR=PyGreSQL-$(PYGRESQL_VERSION)
 pygresql:
 	@echo "--- PyGreSQL"

ext @ ae1a142b

-Subproject commit 3351cf76d50e150ef5d3e9bf7a5d85cd7af0a2c8
+Subproject commit ae1a142be5e139ffec555e8d004ade56e8b98ce2

python-dependencies.txt

@@ -8,5 +8,6 @@ MarkupSafe==1.0
 mock==1.0.1
 parse==1.8.2
 psutil==5.7.0
+pygresql==5.2
 setuptools==36.6.0
 unittest2==0.5.1