Revert "Update .asf.yaml to enable merge java_release_5.0.6 (#686)" (#687)

This reverts commit 79582e428e01f45653f384e980643e14193db2b8.
diff --git a/.asf.yaml b/.asf.yaml
index 1401283..4f5661e 100644
--- a/.asf.yaml
+++ b/.asf.yaml
@@ -33,7 +33,7 @@
     # Enable squash button
     squash: true
     # Disable merge button
-    merge: true
+    merge: false
     # Disable rebase button
     rebase: false
   protected_branches: