Fix Cover block backround (#7996)

* Update theme.json to fix https://github.com/Automattic/wp-calypso/issues/84247

* Update theme.json

eventual/theme.json

@@ -235,11 +235,6 @@
 					}
 				}
 			},
-			"core/cover": {
-				"color": {
-					"text": "var(--wp--preset--color--base)"
-				}
-			},
 			"core/gallery": {
 				"spacing": {
 					"margin": {
@@ -654,4 +649,4 @@
 	],
 	"version": 2,
 	"$schema": "https://schemas.wp.org/trunk/theme.json"
-}
+}