openssl: do not set SSL_MODE_RELEASE_BUFFERS

While it might save some memory, it causes OpenSSL to instead do a huge
amount of allocations.

Ref: #13136
Closes #13203

lib/vtls/openssl.c

@@ -3565,10 +3565,6 @@ static CURLcode ossl_connect_step1(struct Curl_cfilter *cf,
     return CURLE_OUT_OF_MEMORY;
   }
 
-#ifdef SSL_MODE_RELEASE_BUFFERS
-  SSL_CTX_set_mode(backend->ctx, SSL_MODE_RELEASE_BUFFERS);
-#endif
-
 #ifdef SSL_CTRL_SET_MSG_CALLBACK
   if(data->set.fdebug && data->set.verbose) {
     /* the SSL trace callback is only used for verbose logging */