Clean symbol export on mod mock

Merge from Widevine repo of http://go/wvgerrit/42281

This cleans up some of the oemcrypto mock code.  This code is only
used for testing.

bug: 72831885
bug: 69271232
Change-Id: I8add162839d6febe56a89df84e8ae0cf0b97a2d9

libwvdrmengine/oemcrypto/mock/src/oemcrypto_session.cpp

@@ -43,15 +43,6 @@ void ctr128_inc64(uint8_t* counter) {
     if (++counter[--n] != 0) return;
   } while (n > 8);
 }
-
-void dump_boringssl_error() {
-  while (unsigned long err = ERR_get_error()) {
-    char buffer[120];
-    ERR_error_string_n(err, buffer, sizeof(buffer));
-    LOGE("BoringSSL Error -- %lu -- %s", err, buffer);
-  }
-}
-
 }  // namespace
 
 namespace wvoec_mock {