fix(da-library): typo in error message for block preview (#749)

https://www.grammarly.com/blog/punctuation-capitalization/slash/#:~:text=When%20a,alternatives%20between

Author: trieloff

blocks/edit/da-library/da-library.js

@@ -386,7 +386,7 @@ class DaLibrary extends LitElement {
           data-src="${this._blockPreviewPath}"
           src="${this._blockPreviewPath}"
           @load=${this.handlePreviewLoad}
-          allow="clipboard-write *"></iframe>` : html`<div style="margin: 0 24px">${error || 'This block / template has not been previewed.'}</div>`}
+          allow="clipboard-write *"></iframe>` : html`<div style="margin: 0 24px">${error || 'This block/template has not been previewed.'}</div>`}
       </da-dialog>
     `;
   }