avoid duplicate labels (#82)

diff --git a/migration/src/jira2github_import.py b/migration/src/jira2github_import.py
index 6e3807e..3974d6f 100644
--- a/migration/src/jira2github_import.py
+++ b/migration/src/jira2github_import.py
@@ -208,6 +208,9 @@
             labels.append(f"legacy-jira-resolution:{resolution}")
         if priority:
             labels.append(f"legacy-jira-priority:{priority}")
+        
+        # ensure there are not duplicate labels
+        labels = list(set(labels))
 
         data = {
             "issue": {