Remove deprecated GetStringStrict method alias

All callers have been migrated to GetString.

PiperOrigin-RevId: 973897022

quiche/common/structured_headers.h

diff --git a/quiche/common/structured_headers.h b/quiche/common/structured_headers.h
index 887bb48..4c8b6b2 100644
--- a/quiche/common/structured_headers.h
+++ b/quiche/common/structured_headers.h
@@ -112,12 +112,6 @@
     QUICHE_CHECK(value);
     return *value;
   }
-  // TODO(apaseltiner): Remove this once all callers have been migrated to
-  // `GetString()`.
-  // Deprecated: Use `GetString()` instead.
-  const std::string& GetStringStrict() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
-    return GetString();
-  }
   const std::string& GetString() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
     const auto* value = GetIfString();
     QUICHE_CHECK(value);