src: remove unnecessary call to SSL_get_mode

SSL_set_mode() bit-ORs its argument into the current mode, its not
necessary for to do it ourself (though it doesn't cause harm).

See:
- https://www.openssl.org/docs/man1.1.0/ssl/SSL_set_mode.html
- https://github.com/nodejs/node/blob/0ce615c4af/deps/openssl/openssl/ssl/ssl_lib.c#L2176-L2177

PR-URL: #25711
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/tls_wrap.cc

@@ -112,8 +112,7 @@ void TLSWrap::InitSSL() {
   SSL_set_verify(ssl_.get(), SSL_VERIFY_NONE, crypto::VerifyCallback);
 
 #ifdef SSL_MODE_RELEASE_BUFFERS
-  long mode = SSL_get_mode(ssl_.get());  // NOLINT(runtime/int)
-  SSL_set_mode(ssl_.get(), mode | SSL_MODE_RELEASE_BUFFERS);
+  SSL_set_mode(ssl_.get(), SSL_MODE_RELEASE_BUFFERS);
 #endif  // SSL_MODE_RELEASE_BUFFERS
 
   SSL_set_app_data(ssl_.get(), this);