fixing issue with instructor service not being loaded in studio

was causing issues with PT exam configuration dashboard launch

requirements/constraints.txt

@@ -43,4 +43,7 @@ oauthlib==2.1.0
 pytest-randomly<2.0.0
 
 # Tornado dropped support for Python 2.7 and 3.4 with version 6.0. Only Python 3.5.2+ is now supported
-tornado<6.0
+tornado<6.0
+
+# Preventing https://github.com/edx/edx-proctoring/pull/557 being installed before https://github.com/edx/edx-platform/pull/19959
+edx-proctoring==1.5.21

requirements/edx/base.txt

@@ -120,7 +120,7 @@ edx-oauth2-provider==1.2.2
 edx-opaque-keys[django]==0.4.4
 edx-organizations==1.0.1
 edx-proctoring-proctortrack==1.0.4
-edx-proctoring==1.6.0
+edx-proctoring==1.5.21
 edx-rbac==0.1.5           # via edx-enterprise
 edx-rest-api-client==1.9.2
 edx-search==1.2.2

requirements/edx/development.txt

@@ -143,7 +143,7 @@ edx-oauth2-provider==1.2.2
 edx-opaque-keys[django]==0.4.4
 edx-organizations==1.0.1
 edx-proctoring-proctortrack==1.0.4
-edx-proctoring==1.6.0
+edx-proctoring==1.5.21
 edx-rbac==0.1.5
 edx-rest-api-client==1.9.2
 edx-search==1.2.2

requirements/edx/testing.txt

@@ -139,7 +139,7 @@ edx-oauth2-provider==1.2.2
 edx-opaque-keys[django]==0.4.4
 edx-organizations==1.0.1
 edx-proctoring-proctortrack==1.0.4
-edx-proctoring==1.6.0
+edx-proctoring==1.5.21
 edx-rbac==0.1.5
 edx-rest-api-client==1.9.2
 edx-search==1.2.2

setup.py

@@ -98,7 +98,8 @@ setup(
             "bookmarks = openedx.core.djangoapps.bookmarks.apps:BookmarksConfig",
             "zendesk_proxy = openedx.core.djangoapps.zendesk_proxy.apps:ZendeskProxyConfig",
             "password_policy = openedx.core.djangoapps.password_policy.apps:PasswordPolicyConfig",
-            "user_authn = openedx.core.djangoapps.user_authn.apps:UserAuthnConfig"
+            "user_authn = openedx.core.djangoapps.user_authn.apps:UserAuthnConfig",
+            "instructor = lms.djangoapps.instructor.apps:InstructorConfig",
         ],
     }
 )