Remove INSTALLED_VBMETAIMAGE_TARGET dependency from target-files.zip

Remove the INSTALLED_VBMETAIMAGE_TARGET, which depends on all the
other images, it is no longer necessary after
If1eff317621882994e7dcbf37cd35f5bfa16b69a.  This will allow the
next change to parallelize target-files.zip with the image generation
rules.

Test: treehugger
Change-Id: Ie27bdbd2d414e9b475823639a1b3944fe0756d2a
diff --git a/core/Makefile b/core/Makefile
index 73f2f7a..a02e2a6 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -4290,7 +4290,6 @@
 	    $(INSTALLED_VENDORIMAGE_TARGET) \
 	    $(INSTALLED_PRODUCTIMAGE_TARGET) \
 	    $(INSTALLED_SYSTEM_EXTIMAGE_TARGET) \
-	    $(INSTALLED_VBMETAIMAGE_TARGET) \
 	    $(INSTALLED_ODMIMAGE_TARGET) \
 	    $(INSTALLED_VENDOR_DLKMIMAGE_TARGET) \
 	    $(INSTALLED_ODM_DLKMIMAGE_TARGET) \