Accesibility icon not being shown in a custom admin theme

Issue

We've created a custom admin-theme but when we go to Instance Settings or System settings, it doesn't show some icons, p.e: accesibility icon.

Having the correct icons available in your theme is dependent on having the correct versions of liferay-frontend-theme-styled and liferay-frontend-theme-unstyled in your package.json.
You can check the versions of those themes from Control Panel -> GoGo shell using below command:
```
lb styled
```
After that, adjust those versions in your custom theme's package.json. Per example, for Liferay DXP 7.4 u86 the values are:
```
"liferay-frontend-theme-styled": "6.0.67",
"liferay-frontend-theme-unstyled": "6.0.55",        
```
After adjusting the versions run the following commands
- If you are using npm:
```
npm install && npm run build
```
- If you are using yarn:
```
yarn && yarn deploy
```

Deploy the new built theme in your Liferay installation and check if this solve the issue.