Fix/post title borders in code editor (#14771)

* Remove thick left border for the title in the code editor.

* Remove thick left border from the permalink field in the code editor.

* Move styles into the `edit-post` module.

* Remove no-longer-necessary style change.

* Remove unnecessary styles.

packages/edit-post/src/components/text-editor/style.scss

@@ -34,16 +34,26 @@
 			padding: $block-padding;
 		}
 
+		// Hide the thick left border in the code editor.
+		&:not(.is-focus-mode):not(.has-fixed-toolbar):not(.is-selected) .editor-post-title__input:hover,
+		&:not(.is-focus-mode):not(.has-fixed-toolbar).is-selected .editor-post-title__input {
+			box-shadow: none;
+			border-left-width: $border-width;
+		}
+
 		textarea:hover,
 		&.is-selected textarea {
 			box-shadow: 0 0 0 $border-width $light-gray-500;
 		}
 	}
 
 	.editor-post-permalink {
-		left: 0;
-		right: 0;
 		margin-top: -6px;
+
+		// Hide the thick left border in the code editor.
+		box-shadow: none;
+		border: none;
+		outline: $border-width solid $light-gray-800;
 	}
 
 	@include break-small() {