update_payload: Remove signature version checking

aosp/1130669 deprecated the 'version' field from the Signatures
message. But the update_payload code wasn't updated, so this CL removes
that check.

BUG=b:169526824
TEST=cros_generate_update_payload --debug --tgt-image dlc.img --src-image dlc.img --output delta.bin --private-key ~/.ssh/testing_rsa  --check

Change-Id: I20aca13eeb33c5c1d2aa72513649198868ab00be
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2434552
Tested-by: Amin Hassani <ahassani@chromium.org>
Auto-Submit: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
diff --git a/scripts/update_payload/checker.py b/scripts/update_payload/checker.py
index 4c65516..58ad85c 100644
--- a/scripts/update_payload/checker.py
+++ b/scripts/update_payload/checker.py
@@ -1148,17 +1148,13 @@
       sig_report = report.AddSubReport(sig_name)
 
       # Check: Signature contains mandatory fields.
-      self._CheckMandatoryField(sig, 'version', sig_report, sig_name)
       self._CheckMandatoryField(sig, 'data', None, sig_name)
       sig_report.AddField('data len', len(sig.data))
 
       # Check: Signatures pertains to actual payload hash.
-      if sig.version == 1:
+      if sig.data:
         self._CheckSha256Signature(sig.data, pubkey_file_name,
                                    payload_hasher.digest(), sig_name)
-      else:
-        raise error.PayloadError('Unknown signature version (%d).' %
-                                 sig.version)
 
   def Run(self, pubkey_file_name=None, metadata_sig_file=None, metadata_size=0,
           part_sizes=None, report_out_file=None):