Remove unused OmitDefault template function from blind_sign_auth.cc.

This template function was unused.

This will become a compilation error in the next portable LLVM release: http://fusion2/presubmit/960538151/OCL:960538151:BASE:960748198:1786087234016:1f3b205f;filter=;groups=NewlyBroken,PossiblyNewlyFailing/targets/invocations/f7a5ef5f-684d-4617-9488-2c5866cb31d6/targets/%2F%2Fthird_party%2Fquiche%2Fblind_sign_auth:blind_sign_auth/log

Tested:
  blaze build //third_party/quiche/blind_sign_auth:blind_sign_auth
  blaze test //third_party/quiche/blind_sign_auth/...
PiperOrigin-RevId: 962325466

quiche/blind_sign_auth/blind_sign_auth.cc

diff --git a/quiche/blind_sign_auth/blind_sign_auth.cc b/quiche/blind_sign_auth/blind_sign_auth.cc
index 767a192..ac31c55 100644
--- a/quiche/blind_sign_auth/blind_sign_auth.cc
+++ b/quiche/blind_sign_auth/blind_sign_auth.cc
@@ -40,11 +40,6 @@
 namespace quiche {
 namespace {
 
-template <typename T>
-std::string OmitDefault(T value) {
-  return value == 0 ? "" : absl::StrCat(value);
-}
-
 constexpr absl::string_view kIssuerHostname =
     "https://ipprotection-ppissuer.googleapis.com";
 constexpr size_t kExpectedExtensionTypesSize = 5;