Fix owners-autoassign ReviewerState field type in project config

The ReviewerState was rendered as a general string in the projecyt
config screen making it error-prone. Change the configuration entry
type to a LIST so that it becomes clear what are the only allowed
values.

Change-Id: I3f1e4468fda030559c6c094ea7b750d30a837b89
diff --git a/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/AutoassignConfigModule.java b/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/AutoassignConfigModule.java
index 5536ebc..dfa812d 100644
--- a/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/AutoassignConfigModule.java
+++ b/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/AutoassignConfigModule.java
@@ -40,7 +40,7 @@
             new ProjectConfigEntry(
                 "Auto-assign field",
                 ReviewerState.REVIEWER.name(),
-                ProjectConfigEntryType.STRING,
+                ProjectConfigEntryType.LIST,
                 Arrays.asList(ReviewerState.CC.name(), ReviewerState.REVIEWER.name()),
                 true,
                 "Change field to use for the assigned accounts"));