Fix typo in optionsPrototype.json5

Change-Id: Ieb9a511dbfa73ef068b612c3aad7711bf33e4709
diff --git a/src/common/optionsPrototype.json5 b/src/common/optionsPrototype.json5
index 79569aa..1b114a4 100644
--- a/src/common/optionsPrototype.json5
+++ b/src/common/optionsPrototype.json5
@@ -140,7 +140,7 @@
     killSwitchType: 'option',
   },
   'flattenthreads': {
-    defaultVale: false,
+    defaultValue: false,
     context: 'options',
     killSwitchType: 'option',
   },