[abi] jmp_buf size ABI transition, phase 3

This completes a soft transition to change the size of
the jmp_buf type in the AArch64 Zircon libc ABI.  The old
ABI is no longer accepted by libc-tests.

Bug: ZX-1947 #comment [libc-tests] complete soft transition for jmp_buf ABI
Change-Id: If4a3edb7e1163a821fd2d0ebdd126c20abda5686
diff --git a/third_party/nacl-ported-tests/abi/abi.cc b/third_party/nacl-ported-tests/abi/abi.cc
index a766a6f..16769d2 100644
--- a/third_party/nacl-ported-tests/abi/abi.cc
+++ b/third_party/nacl-ported-tests/abi/abi.cc
@@ -104,10 +104,7 @@
   CHECK_SIZEOF(struct dirent, 280);
 
 #if defined(__aarch64__)
-  // TODO(ZX-1947): Soft transition adding a word to jmp_buf.
-  if (sizeof(jmp_buf) != 312) {
-    CHECK_SIZEOF(jmp_buf, 320);
-  }
+  CHECK_SIZEOF(jmp_buf, 320);
 #else
   CHECK_SIZEOF(jmp_buf, 208);
 #endif