Update netbeansrelease.json

allow update 12 u1 to build
diff --git a/meta/netbeansrelease.json b/meta/netbeansrelease.json
index 923ad98..640ae18 100644
--- a/meta/netbeansrelease.json
+++ b/meta/netbeansrelease.json
@@ -248,9 +248,9 @@
             }
         },
         "releasedate": {
-            "day": "04",
-            "month": "06",
-            "year": "2020"
+            "day": "-",
+            "month": "-",
+            "year": "-"
         },
         "previousreleasedate": {
             "day": "24",