Pin just edx-drf-extensions.

We also pin back edx-lint to fix a regression we introduced when we
started having to roll back all the requirements changes.

requirements/constraints.txt

@@ -78,7 +78,7 @@ numpy<1.17.0
 jsondiff==1.1.1
 
 
-# Constraining these so that we can slow-roll their deploy to find out which one is causing the production performance issues.
-edx-when==0.4
-edx-enterprise==1.10.8
+# Constraining this because when we rolled it to edx.org production
+# we had a lot of memory issues and gunicorn workers started running
+# out of memory.  ARCH-1210
 edx-drf-extensions==2.4.0

requirements/edx/testing.in

@@ -24,7 +24,7 @@ code-annotations          # Perform code annotation checking, such as for PII an
 cssselect                 # Used to extract HTML fragments via CSS selectors in 2 test cases and pyquery
 ddt                       # Run a test case multiple times with different input; used in many, many of our tests
 edx-i18n-tools>=0.4.6     # Commands for developers and translators to extract, compile and validate translations
-edx-lint==1.4.0           # pylint extensions for Open edX repositories
+edx-lint==1.3.0           # pylint extensions for Open edX repositories
 factory_boy==2.8.1        # Library for creating test fixtures, used in many tests
 freezegun                 # Allows tests to mock the output of assorted datetime module functions
 httpretty                 # Library for mocking HTTP requests, used in many tests