Revert "ART: Check dex file constraint A1"

This will be checked by the method verifier. Checking it in the
structural verifier causes some apps to stop working.

Bug: 140921952
Test: manual

This reverts commit d1abab7110101d65774f9d090850d20aaa07b661.

Change-Id: I3cae361a9ad0f597bcd84d0a538fcf04e448c349
diff --git a/libdexfile/dex/dex_file_verifier.cc b/libdexfile/dex/dex_file_verifier.cc
index 80ab80f..f69b657 100644
--- a/libdexfile/dex/dex_file_verifier.cc
+++ b/libdexfile/dex/dex_file_verifier.cc
@@ -1610,10 +1610,6 @@
 
   const uint16_t* insns = accessor.Insns();
   uint32_t insns_size = accessor.InsnsSizeInCodeUnits();
-  if (insns_size == 0) {
-    ErrorStringPrintf("insns_size must not be zero (%ud)", insns_size);
-    return false;
-  }
   if (!CheckListSize(insns, insns_size, sizeof(uint16_t), "insns size")) {
     return false;
   }