Ensure that we are using SQL storage for taxonomy_update_8007()

#1497374: Switch from Field-based storage to Entity-based storage changed the following checks to ensure that the upgrade is against SQL and not some other storage engines.

+++ b/core/modules/file/file.install
@@ -305,21 +306,21 @@ function file_update_8003() {
-    if (in_array($field_config->get('type'), array('file', 'image')) && $field_config->get('storage.type') == 'field_sql_storage') {
+    if (in_array($field_config->get('type'), array('file', 'image'))) {

+++ b/core/modules/taxonomy/taxonomy.install
@@ -356,16 +361,16 @@ function taxonomy_update_8007() {
-    if ($field_config->get('type') == 'taxonomy_term_reference' && $field_config->get('storage.type') == 'field_sql_storage') {
+    if ($field_config->get('type') == 'taxonomy_term_reference') {
       $field = new Field($field_config->get());

We need to re-instate some from of check - perhaps just check if the tables exist.