Index: wp-includes/css/dist/block-library/theme.css
===================================================================
--- wp-includes/css/dist/block-library/theme.css	(revision 55900)
+++ wp-includes/css/dist/block-library/theme.css	(working copy)
@@ -21,7 +21,7 @@
 .wp-block-embed figcaption{
   color:#555;
   font-size:13px;
-  text-align:center;
+  text-align:center !important;
 }
 .is-dark-theme .wp-block-embed figcaption{
   color:hsla(0,0%,100%,.65);