src: remove unnecessary cast in crypto_sig.cc

ByteSource::Allocated accepts a void pointer now, so we do not need to
cast the argument to a char pointer.

Refs: #43202

PR-URL: #44001
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Feng Yu <F3n67u@outlook.com>

src/crypto/crypto_sig.cc

@@ -216,7 +216,7 @@ ByteSource ConvertSignatureToDER(
 
   CHECK_NOT_NULL(data);
 
-  return ByteSource::Allocated(reinterpret_cast<char*>(data), len);
+  return ByteSource::Allocated(data, len);
 }
 
 void CheckThrow(Environment* env, SignBase::Error error) {