keymaster: remove unused kNetError from cert_store.mojom

BUG=b:119914122
TEST=compile

Change-Id: I1aa22d6e468e86abb3dc8947ad4ddf6baca52d15
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2002393Reviewed-by: Greg Kerr <kerrnel@chromium.org>
Commit-Queue: Polina Bondarenko <pbond@chromium.org>
Auto-Submit: Polina Bondarenko <pbond@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732085}

chrome/services/keymaster/public/mojom/cert_store.mojom

@@ -30,8 +30,6 @@ enum SignatureResult {
   kOk,
   // Failed with error.
   kFailed,
-  // Inspect Chrome's logs for the exact net::Error.
-  kNetError,
   kUnsupportedAlgorithm,
 };