Restore compatibility with OpenSSL

During review, I asked Paul to change the call to invalidate the
encoding to use the newer BoringSSL functions. However, OpenSSL doesn't
have these functions so it broke the build with OpenSSL. Restore this
line to Paul's previous patchset to keep OpenSSL working.

Change-Id: I2fe43073db78a783c585c44b186afa634493bf91
diff --git a/src/main/native/org_conscrypt_NativeCrypto.cpp b/src/main/native/org_conscrypt_NativeCrypto.cpp
index 06b62d0..e2ec257 100644
--- a/src/main/native/org_conscrypt_NativeCrypto.cpp
+++ b/src/main/native/org_conscrypt_NativeCrypto.cpp
@@ -6932,7 +6932,11 @@
         X509_EXTENSION_free(ext);
 
         // Invalidate the cached encoding
+#if defined(OPENSSL_IS_BORINGSSL)
         X509_CINF_set_modified(X509_get_cert_info(x509));
+#else
+        x509->cert_info->enc.modified = 1;
+#endif
     }
 }