Remove INCLUDE_TEST_OTA_KEYS.

This has been long dead since commit
17c83cf22c426c628b4b21bc65128a0d80866d31 (2009).

Test: m checkbuild (via TreeHugger)
Test: No hit in code search.
Change-Id: I054241ae63436ade2f4e50ec2fc3757ae35635dd
diff --git a/core/main.mk b/core/main.mk
index 54d7c23..7435eb0 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -317,8 +317,6 @@
   ADDITIONAL_DEFAULT_PROPERTIES += ro.debuggable=1
   # Enable Dalvik lock contention logging.
   ADDITIONAL_BUILD_PROPERTIES += dalvik.vm.lockprof.threshold=500
-  # Include the debugging/testing OTA keys in this build.
-  INCLUDE_TEST_OTA_KEYS := true
 else # !enable_target_debugging
   # Target is less debuggable and adbd is off by default
   ADDITIONAL_DEFAULT_PROPERTIES += ro.debuggable=0