reverts change from method setViewer back to setUser because of upstream inconsistency

there continues to be upstream confusion between "viewer" and "user", it seems that ConduitAPIRequest does not support "viewer"...

Change-Id: I03e9b9c625d3ae86f222d1e901cd6afb29080888

src/conduit/SprintCreateConduitAPIMethod.php

@@ -28,7 +28,7 @@ final class SprintCreateConduitAPIMethod extends SprintConduitAPIMethod {
   }
 
   protected function execute(ConduitAPIRequest $request) {
-    $user = $request->getViewer();
+    $user = $request->getUser();
 
     $this->requireApplicationCapability(
       ProjectCreateProjectsCapability::CAPABILITY,

src/conduit/SprintGetStartEndDatesConduitAPIMethod.php

@@ -25,7 +25,7 @@ final class SprintGetStartEndDatesConduitAPIMethod extends SprintConduitAPIMetho
   }
 
   protected function execute(ConduitAPIRequest $request) {
-    $user = $request->getViewer();
+    $user = $request->getUser();
     $query = id(new SprintQuery())
         ->setViewer($user);
     $project = id(new PhabricatorProjectQuery())

src/conduit/SprintGetTaskProjectHistoryConduitAPIMethod.php

@@ -25,7 +25,7 @@ final class SprintGetTaskProjectHistoryConduitAPIMethod extends SprintConduitAPI
   }
 
   protected function execute(ConduitAPIRequest $request) {
-    $user = $request->getViewer();
+    $user = $request->getUser();
 
     $this->requireApplicationCapability(
         ProjectCreateProjectsCapability::CAPABILITY,

src/conduit/SprintSetIsSprintConduitAPIMethod.php

@@ -26,7 +26,7 @@ final class SprintSetIsSprintConduitAPIMethod extends SprintConduitAPIMethod {
   }
 
   protected function execute(ConduitAPIRequest $request) {
-    $user = $request->getViewer();
+    $user = $request->getUser();
 
     $this->requireApplicationCapability(
         ProjectCreateProjectsCapability::CAPABILITY,

src/conduit/SprintSetStartEndDatesConduitAPIMethod.php

@@ -27,7 +27,7 @@ final class SprintSetStartEndDatesConduitAPIMethod extends SprintConduitAPIMetho
   }
 
   protected function execute(ConduitAPIRequest $request) {
-    $user = $request->getViewer();
+    $user = $request->getUser();
 
     $this->requireApplicationCapability(
         ProjectCreateProjectsCapability::CAPABILITY,