Update NHS Frontend to 9.1.0 (#133)

Main difference is a change in alignment in the header for the nav.


## Screenshots

### Before

<img width="982" alt="Screenshot 2024-11-05 at 14 48 04"
src="https://github.com/user-attachments/assets/c97053c3-d54a-4d84-93d3-fe3e73a2dee7">

### After

<img width="994" alt="Screenshot 2024-11-05 at 14 47 30"
src="https://github.com/user-attachments/assets/9b8ba392-28ae-47fe-b0a1-1b1b238330f0">

package.json

@@ -34,7 +34,7 @@
     "gulp-rename": "^2.0.0",
     "gulp-sass": "^5.1.0",
     "lodash": "^4.17.21",
-    "nhsuk-frontend": "^9.0.0",
+    "nhsuk-frontend": "^9.1.0",
     "nunjucks": "^3.2.4",
     "path": "^0.12.7",
     "sass": "^1.77.8"